Elastic wave device with sub-wavelength thick piezoelectric layer

ABSTRACT

Aspects of this disclosure relate to an elastic wave device. The elastic wave device includes a sub-wavelength thick piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and a high velocity layer with a higher bulk velocity than the velocity of an elastic wave.

CROSS REFERENCE TO PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR § 1.57.This application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Patent Application No. 62/410,804, filed Oct. 20,2016 and titled “ELASTIC WAVE DEVICE,” the disclosure of which is herebyincorporated by reference in its entirety herein. This applicationclaims the benefit of priority under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application No. 62/423,705, filed Nov. 17, 2016 andtitled “ELASTIC WAVE DEVICE,” the disclosure of which is herebyincorporated by reference in its entirety herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to an elastic wave device.

Description of Related Technology

An elastic wave device can implement a surface acoustic wave resonator.A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed. Surface acoustic wave resonators can implement a surfaceacoustic wave filter.

Surface acoustic wave resonators can be implemented in radio frequencyelectronic systems. For instance, filters in a radio frequency front endof a mobile phone can include surface acoustic wave filters. Designing asurface acoustic wave resonator that meets or exceeds the designspecifications for such radio frequency systems can be challenging.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several features, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

One aspect of this disclosure is an elastic wave device that includes apiezoelectric layer, an interdigital transducer electrode on thepiezoelectric layer, and a high velocity layer in physical contact withthe piezoelectric layer. The piezoelectric layer has a cut angle in acut angle range from −10° to 60°. The interdigital transducer electrodeis configured to generate an elastic wave having a wavelength of λ. Thepiezoelectric layer has a thickness in a thickness range from 0.35λ to0.8λ. The high velocity layer has a higher bulk velocity than a velocityof the elastic wave.

The piezoelectric layer can include a lithium niobate layer. Thepiezoelectric layer can include a lithium tantalate layer. The thicknessof the piezoelectric layer can be in a range from 0.4λ to 0.75λ.

The high velocity layer can be a silicon layer.

The cut angle of the piezoelectric layer can be in a range from −10° to50°. The cut angle of the piezoelectric layer can be in a range from−10° to 30°. The cut angle of the piezoelectric layer can be in a rangefrom 0° to 30°. The cut angle of the piezoelectric layer can be in arange from 10° to 30°. The cut angle of the piezoelectric layer can bein a range from 20° to 30°. The cut angle of the piezoelectric layer canbe in a range from 30° to 40°.

The interdigital transducer electrode can include aluminum. In someinstances, the material of the interdigital transducer electrode can bean aluminum alloy. The interdigital transducer electrode can have athickness in a second thickness range from 0.02λ to 0.1λ.

The elastic wave device can further include a temperature compensatinglayer arranged such that the interdigital transducer electrode isdisposed between the temperature compensating layer and thepiezoelectric layer. The temperature compensating layer can includesilicon dioxide. The temperature compensating layer can have a thicknessof less than 0.5λ.

Another aspect of this disclosure is an elastic wave device thatincludes a lithium niobate layer, an interdigital transducer electrodeon the lithium niobate layer, and a silicon substrate in physicalcontact with the lithium niobate layer. The lithium niobate layer has acut angle in a cut angle range from −10° to 60°. The interdigitaltransducer electrode is configured to generate an elastic wave having awavelength of λ. The lithium niobate layer has a thickness in athickness range from 0.35λ to 0.8λ.

The cut angle of the lithium niobate layer can be a range from −10° to30°. The cut angle of the lithium niobate layer can be a range from 15°to 35°. The cut angle of the lithium niobate layer can be a range from20° to 30°.

The thickness of the lithium niobate layer can be in a range from 0.4λto 0.75λ.

The interdigital transducer electrode can include aluminum. Theinterdigital transducer electrode can have a thickness in a secondthickness range from 0.02λ to 0.1λ.

The elastic wave device can further include a temperature compensatinglayer arranged such that the interdigital transducer electrode isdisposed between the temperature compensating layer and the lithiumniobate layer. The temperature compensating layer can include silicondioxide. The temperature compensating layer can have a thickness of lessthan 0.5λ.

Another aspect of this disclosure is an elastic wave device thatincludes a lithium niobate layer, an interdigital transducer electrodeon the lithium niobate layer, a high velocity layer having a higher bulkvelocity than a velocity of the elastic wave, and a temperaturecompensating layer disposed between the high velocity layer and thelithium niobate layer. The lithium niobate layer has a cut angle in acut angle range from −10° to 60°. The interdigital transducer electrodeis configured to generate an elastic wave having a wavelength of λ. Thelithium niobate layer has a thickness in a thickness range from 0.35λ to0.8λ. The high velocity layer is configured to inhibit the elastic wavefrom leaking from the lithium niobate layer at anti-resonance. Thetemperature compensating layer has a positive temperature coefficient offrequency. The elastic wave device is arranged so as to have anelectromechanical coupling coefficient of at least 26%.

The high velocity layer can be a silicon layer.

The temperature compensating layer can be a silicon dioxide layer. Thetemperature compensating layer can have a thickness of less than 0.5λ.

The interdigital transducer electrode can include aluminum.

The cut angle of the lithium niobate layer can be in a range from 15° to35°. The cut angle of the lithium niobate layer can be in a range from20° to 30°. The cut angle of the lithium niobate layer can be in a rangefrom −10° to 30°.

The thickness of the lithium niobate layer can be in a range from 0.4λto 0.75λ.

The electromechanical coupling coefficient can be at least 28%. Theelectromechanical coupling coefficient can be less than 30%. Theelectromechanical coupling coefficient can be less than 35%.

A quality factor of the acoustic wave device can be in a range from 2000to 5000.

Another aspect of this disclosure is an elastic wave device thatincludes a lithium tantalate layer, an interdigital transducer electrodeon the lithium tantalate layer, a high velocity layer having a higherbulk velocity than a velocity of the elastic wave, and a temperaturecompensating layer disposed between the high velocity layer and thelithium tantalate layer. The lithium tantalate layer has a cut angle ina cut angle range from −10° to 50°. The interdigital transducerelectrode is configured to generate an elastic wave having a wavelengthof λ. The lithium tantalate layer has a thickness that is less than k.The high velocity layer is configured to inhibit the elastic wave fromleaking from the lithium tantalate layer at anti-resonance. Thetemperature compensating layer has a positive temperature coefficient offrequency.

The high velocity layer can be a silicon layer.

The temperature compensating layer can be a silicon dioxide layer. Thetemperature compensating layer can have a thickness of less than 0.5λ.

The interdigital transducer electrode can include aluminum. Theinterdigital transducer electrode can have a thickness in a secondthickness range from 0.02λ to 0.1λ.

The cut angle of the lithium tantalate layer can be in a range from −10°to 30°. The cut angle of the lithium tantalate layer can be in a rangefrom 0° to 30°. The cut angle of the lithium tantalate layer can be in arange from 10° to 30°. The cut angle of the lithium tantalate layer canbe in a range from 30° to 40°. The cut angle of the lithium tantalatelayer can be in a range from 15° to 35°. The cut angle of the lithiumtantalate layer can be in a range from 20° to 30°.

The thickness of the lithium tantalate layer can be in a range from0.25λ to 0.8λ. The thickness of the lithium tantalate layer can be in arange from 0.35λ to 0.8λ. The thickness of the lithium tantalate layercan be in a range from 0.4λ to 0.75λ.

Another aspect of this disclosure is an elastic wave device thatincludes a piezoelectric layer, an interdigital transducer electrode onthe piezoelectric layer, and a high velocity layer having a higher bulkvelocity than a velocity of the elastic wave and being configured toinhibit the elastic wave from leaking from the piezoelectric layer atanti-resonance. The piezoelectric layer has a cut angle in a cut anglerange from −10° to 60°. The interdigital transducer electrode isconfigured to generate an elastic wave having a wavelength of λ. Theinterdigital transducer electrode has a thickness in a first thicknessrange from 0.02λ to 0.1λ. The piezoelectric layer has a thickness thatis less than k.

The high velocity layer can be a silicon layer.

The piezoelectric layer can include a lithium niobate layer. Thepiezoelectric layer can include a lithium tantalate layer.

The thickness of the interdigital transducer electrode can be between0.05λ and 0.1λ. The interdigital transducer electrode can includealuminum.

The cut angle of the piezoelectric layer can be in a range from −10° to30°. The cut angle of the piezoelectric layer can be in a range from 0°to 30°. The cut angle of the piezoelectric layer can be in a range from15° to 35°. The cut angle of the piezoelectric layer can be in a rangefrom 20° to 30°. The cut angle of the piezoelectric layer can be in arange from 30° to 40°.

The thickness of the piezoelectric layer can be in a second thicknessrange from 0.25λ to 0.8λ. The thickness of the piezoelectric layer canbe in a range from 0.35λ to 0.8λ. The thickness of the piezoelectriclayer can be range from 0.4λ to 0.75λ.

The high velocity layer can be bonded to and in physical contact withthe piezoelectric layer. The high velocity layer can be a siliconsubstrate.

The elastic wave device can further include a temperature compensatinglayer disposed between the high velocity layer and the piezoelectriclayer. The temperature compensating layer can include silicon dioxide.The temperature compensating layer can have a thickness of less than0.5λ.

The elastic wave device can further include a temperature compensatinglayer arranged such that the interdigital transducer electrode isdisposed between the temperature compensating layer and thepiezoelectric layer. The temperature compensating layer can includesilicon dioxide. The temperature compensating layer can have a thicknessof less than 0.5λ.

Another aspect of this disclosure is an elastic wave device thatincludes a piezoelectric layer, an interdigital transducer electrode onthe piezoelectric layer, a silicon layer configured to inhibit theelastic wave from leaking from the piezoelectric layer atanti-resonance, and a temperature compensating layer having a positivetemperature coefficient of frequency. The piezoelectric layer has a cutangle in a cut angle range from −10° to 60°. The interdigital transducerelectrode is configured to generate an elastic wave having a wavelengthof λ. The piezoelectric layer has a thickness in a thickness range from0.25λ to 0.8λ. The piezoelectric layer is disposed between the siliconlayer and the interdigital transducer electrode. The interdigitaltransducer electrode is disposed between the temperature compensatinglayer and the piezoelectric layer.

The temperature compensating layer can have a thickness of less than0.5λ. The temperature compensating layer can include silicon dioxide.The temperature compensating layer can include tellurium dioxide. Thetemperature compensating layer can include SiOF.

The cut angle of the piezoelectric layer can be between −10° and 30°.The cut angle of the piezoelectric layer can be between 15° and 35°. Thecut angle of the piezoelectric layer can be between 20° and 30°.

The thickness of the piezoelectric layer can be between 0.35λ to 0.8λ.The thickness of the piezoelectric layer can be between 0.4λ to 0.75λ.

The interdigital transducer electrode can have a thickness between 0.02λand 0.1λ. The interdigital transducer electrode can include aluminum.

The piezoelectric layer can be a lithium niobate layer. Thepiezoelectric layer can be a lithium tantalate layer.

The silicon layer can be physical contact with the piezoelectric layer.

A filter can include an elastic wave device in accordance with anysuitable principles and advantages discussed herein. A duplexer caninclude an elastic wave device in accordance with any suitableprinciples and advantages discussed herein.

A packaged module can include an elastic wave device in accordance withany suitable principles and advantages discussed herein. The packagedmodule can further include a radio frequency switch. The packaged modulecan further include a power amplifier.

A wireless communication device can include an elastic wave device inaccordance with any suitable principles and advantages discussed herein.The wireless communication device can be a mobile phone. The elasticwave device can be included in a filter and/or a frequency multiplexingcircuit, such as a duplexer.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

The present disclosure relates to U.S. patent application Ser. No.15/787,596, titled “ELASTIC WAVE DEVICE WITH SUB-WAVELENGTH THICKPIEZOELECTRIC LAYER AND HIGH VELOCITY LAYER,” filed on even dateherewith, the entire disclosure of which is hereby incorporated byreference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will be described, by way of non-limitingexample, with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of an elastic wave device according toan embodiment.

FIGS. 2A to 2E are graphs of simulations of an elastic wave device ofFIG. 1 that includes a lithium tantalate piezoelectric layer on asilicon substrate, in which a thickness of the lithium tantalatepiezoelectric layer is varied. FIG. 2A is a graph of a frequencyresponse for various lithium tantalate thicknesses and for acorresponding device without a silicon substrate. FIG. 2B is a graph ofelectromechanical coupling coefficient versus lithium tantalatethickness. FIG. 2C is a graph of quality factor versus lithium tantalatethickness. FIG. 2D is a graph of figure of merit versus lithiumtantalate thickness. FIG. 2E is a graph of velocity versus lithiumtantalate thickness.

FIGS. 3A to 3E are graphs of simulations of an elastic wave device ofFIG. 1 that includes a lithium tantalate piezoelectric layer on asilicon substrate, in which a thickness of an interdigital transducerelectrode is varied. FIG. 3A is a graph of a frequency response forvarious interdigital transducer electrode thicknesses and for acorresponding device without a silicon substrate. FIG. 3B is a graph ofelectromechanical coupling coefficient versus interdigital transducerelectrode thickness. FIG. 3C is a graph of quality factor versusinterdigital transducer electrode thickness. FIG. 3D is a graph offigure of merit versus interdigital transducer electrode thickness. FIG.3E is a graph of velocity versus interdigital transducer electrodethickness.

FIGS. 4A to 4E are graphs of simulations of an elastic wave device ofFIG. 1 that includes a lithium tantalate piezoelectric layer on asilicon substrate, in which a cut angle is varied. FIG. 4A is a graph ofa frequency response for various cut angles and for a correspondingdevice without a silicon substrate. FIG. 4B is a graph ofelectromechanical coupling coefficient versus cut angle. FIG. 4C is agraph of quality factor versus cut angle. FIG. 4D is a graph of figureof merit versus cut angle. FIG. 4E is a graph of velocity versus cutangle.

FIGS. 5A to 5E are graphs of simulations of an elastic wave device ofFIG. 1 that includes a lithium niobate piezoelectric layer on a siliconsubstrate, in which a thickness of the lithium niobate piezoelectriclayer is varied. FIG. 5A is a graph of a frequency response for variouslithium niobate thicknesses and for a corresponding device without asilicon substrate. FIG. 5B is a graph of electromechanical couplingcoefficient versus lithium niobate thickness. FIG. 5C is a graph ofquality factor versus lithium niobate thickness. FIG. 5D is a graph offigure of merit versus lithium niobate thickness. FIG. 5E is a graph ofvelocity versus lithium niobate thickness.

FIGS. 6A to 6E are graphs of simulations of an elastic wave device ofFIG. 1 that includes a lithium niobate piezoelectric layer on a siliconsubstrate, in which a thickness of an interdigital transducer electrodeis varied. FIG. 6A is a graph of a frequency response for variousinterdigital transducer electrode thicknesses and for a correspondingdevice without a silicon substrate. FIG. 6B is a graph ofelectromechanical coupling coefficient versus interdigital transducerelectrode thickness. FIG. 6C is a graph of quality factor versusinterdigital transducer electrode thickness. FIG. 6D is a graph offigure of merit versus interdigital transducer electrode thickness. FIG.6E is a graph of velocity versus interdigital transducer electrodethickness.

FIGS. 7A to 7E are graphs of simulations of an elastic wave device ofFIG. 1 that includes a lithium niobate piezoelectric layer on a siliconsubstrate, in which a cut angle is varied. FIG. 7A is a graph of afrequency response for various cut angles and for a corresponding devicewithout a silicon substrate. FIG. 7B is a graph of electromechanicalcoupling coefficient versus cut angle. FIG. 7C is a graph of qualityfactor versus cut angle. FIG. 7D is a graph of figure of merit versuscut angle. FIG. 7E is a graph of velocity versus cut angle.

FIGS. 8A to 8F compare simulation results for an elastic wave device ofFIG. 1 that includes a lithium tantalate piezoelectric layer with anelastic wave device of FIG. 1 that includes a lithium niobatepiezoelectric layer. FIG. 8A is a graph of electromechanical couplingcoefficient versus piezoelectric layer thickness. FIG. 8B is a graph ofelectromechanical coupling coefficient versus interdigital transducerelectrode thickness. FIG. 8C is a graph of electromechanical couplingcoefficient versus cut angle. FIG. 8D is a graph of figure of meritversus piezoelectric layer thickness. FIG. 8E is a graph of figure ofmerit versus interdigital transducer electrode thickness. FIG. 8F is agraph of figure of merit versus cut angle.

FIG. 9 is a graph of phase velocity versus piezoelectric layer thicknessfor an elastic wave device of FIG. 1 with an LT piezoelectric layer witha 42° cut angle on a silicon substrate.

FIG. 10 is a graph of k² versus piezoelectric layer thickness for anelastic wave device of FIG. 1 with an LT piezoelectric layer with a 42°cut angle on a silicon substrate.

FIG. 11A is a graph of the quality factor versus piezoelectric layerthickness for an elastic wave device of FIG. 1 with an LT piezoelectriclayer with a 42° cut angle on a silicon substrate. FIG. 11B is a graphthat illustrates that waves can be trapped on the surface of an elasticwave device of FIG. 1 with an LT piezoelectric layer with a 42° cutangle on a silicon substrate. FIG. 11C illustrates that elastic wavescan leak into the substrate for a similar elastic wave device that doesnot include a silicon substrate.

FIGS. 12A to 12D illustrate spurious modes for an elastic wave device ofFIG. 1 with an LT piezoelectric layer on silicon substrate. FIG. 12Aillustrates a spurious mode for a lithium tantalate thickness of 0.05λ.FIG. 12B illustrates a spurious mode for a lithium tantalate thicknessof 0.75λ. FIG. 12C illustrates a spurious mode for a lithium tantalatethickness of 0.25λ. FIG. 12D illustrates a spurious mode for a lithiumtantalate thickness of 1λ.

FIGS. 13A to 13C illustrate an impact of the thickness of an aluminumIDT electrode on an elastic wave device of FIG. 1 with an LTpiezoelectric layer on a silicon substrate for various thicknesses ofthe LT layer. FIG. 13A illustrates an impact of IDT electrode thicknesson Q. FIG. 13B illustrates an impact of IDT electrode thickness on phasevelocity (Vp). FIG. 13C illustrates an impact of IDT electrode thicknesson k².

FIG. 14A illustrates normalized average surface displacement fp for anelastic wave device with a lithium niobate substrate. FIG. 14Billustrates normalized average surface displacement fp for an elasticwave device of FIG. 1 with a lithium niobate substrate on a siliconsubstrate.

FIGS. 15A to 15D are graphs for simulations of an elastic wave device ofFIG. 1 with an LN piezoelectric layer on a silicon substrate forthickness of the LN layer and various parameters. FIG. 15A illustratesk² as a function of thickness of the LN layer.

FIG. 15B illustrates Qp as a function of thickness of the LN layer. FIG.15C illustrates Qs as a function of thickness of the LN layer. FIG. 15Dillustrates v₀ as a function of thickness of the LN layer.

FIGS. 16A to 16K are graphs of admittance over frequency for an elasticwave device of FIG. 1 with an LN piezoelectric layer on a siliconsubstrate for various cut angles of the LN piezoelectric layer. FIG. 16Acorresponds to a cut angle of −30°. FIG. 16B corresponds to a cut angleof −20°. FIG. 16C corresponds to a cut angle of −10°. FIG. 16Dcorresponds to a cut angle of 0°. FIG. 16E corresponds to a cut angle of10°. FIG. 16F corresponds to a cut angle of 20°. FIG. 16G corresponds toa cut angle of 30°. FIG. 16H corresponds to a cut angle of 40°. FIG. 16Icorresponds to a cut angle of 50°. FIG. 16J corresponds to a cut angleof 60°. FIG. 16K corresponds to a cut angle of 70°.

FIG. 17A is a graph of k² for certain cut angles of an elastic wavedevice of FIG. 1 with a high velocity layer that is a silicon substrate.

FIG. 17B is a graph of v₀ for certain cut angles of an elastic wavedevice of FIG. 1 with a high velocity layer that is a silicon substrate.

FIG. 18A to 18C are graphs for simulations of an elastic wave device ofFIG. 1 with an LN piezoelectric layer having a 128° cut angle on asilicon substrate. FIG. 18A illustrates a frequency response for a LNlayer having a thickness of 0.7λ. FIG. 18B illustrates a frequencyresponse for a LN layer having a thickness of 1λ. FIG. 18C illustrates afrequency response for a LN layer having a theoretically infinitethickness.

FIG. 19 is a graph of velocity of the elastic wave device of FIG. 1 as afunction of thickness of the piezoelectric layer.

FIGS. 20A and 20B are graphs for simulations of Q as a function ofthickness of the piezoelectric layer of an elastic wave device of FIG. 1for certain piezoelectric layers on a silicon substrate. FIG. 20A is agraph of Qs as a function of thickness of certain piezoelectric layers.FIG. 20B is a graph of Qp as a function of thickness of certainpiezoelectric layers.

FIG. 21 is a cross-sectional view of an elastic wave device according toan embodiment.

FIG. 22A is a graph of k² as a function of 42LT thickness for variousthicknesses of a silicon dioxide layer of the elastic wave device ofFIG. 21.

FIG. 22B is a graph of v_(P-OPEN) as a function of 42LT thickness forvarious thicknesses of a silicon dioxide layer of the elastic wavedevice of FIG. 21.

FIG. 23A illustrates a relationship between Qs and 42LT thicknesses forvarious silicon dioxide layer thicknesses of the elastic wave device ofFIG. 21.

FIG. 23B illustrates a relationship between Qp and 42LT thicknesses forvarious silicon dioxide layer thicknesses of the elastic wave device ofFIG. 21.

FIGS. 24A and 24B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer of the elastic wave device of FIG. 21. FIG. 24Acorresponds to 42LT with a thickness of 0.25λ. FIG. 24B corresponds to42LT with a thickness of 0.5λ.

FIGS. 25A to 25C illustrate spurious modes in frequency responses forvarious 42LT and silicon dioxide thicknesses of the elastic wave deviceof FIG. 21. FIG. 25A shows a relatively clean frequency response for a42LT layer with a thickness of 0.15λ and a silicon dioxide thickness of0.2λ. FIG. 25B shows a Rayleigh wave in a pass band when the 42LT layerhas a thickness of less than 0.03λ. FIG. 25C shows a plate wave in apass band when the 42LT layer has a thickness of greater than 0.8λ.

FIG. 26A is a contour plot for Vo for the elastic wave device of FIG.21. FIG. 26B is a contour plot for k² for the elastic wave device ofFIG. 21.

FIG. 27A is a contour plot for Qs for the elastic wave device of FIG.21. FIG. 27B is a contour plot for Qp for the elastic wave device ofFIG. 21.

FIG. 28A is a contour plot for Qavg for the elastic wave device of FIG.21. FIG. 28B is a contour plot for FOM for the elastic wave device ofFIG. 21.

FIGS. 29A to 29D illustrate displacement being confined to the surfaceof the piezoelectric layer for 42LT and 5LN piezoelectric layers in theelastic wave device of FIG. 21 while displacement is not as confined tothe surface in similar elastic wave devices without a high velocitylayer and a temperature compensating layer. FIG. 29A illustratesdisplacement in an elastic wave device with a 42LT substrate. FIG. 29Billustrates displacement in an elastic wave device of FIG. 21 with a42LT piezoelectric layer, a silicon dioxide temperature compensatinglayer, and a high velocity layer that is a silicon substrate. FIG. 29Cillustrates displacement in an elastic wave device with a 5LN substrate.FIG. 29D illustrates displacement in an elastic wave device of FIG. 21with a 5LN piezoelectric layer, a silicon dioxide temperaturecompensating layer, and a high velocity layer that is a siliconsubstrate.

FIG. 30A is a graph of k² as a function of 5LN thickness for variousthicknesses of a silicon dioxide layer of the elastic wave device ofFIG. 21.

FIG. 30B is a graph of v_(P-OPEN) as a function of 5LN thickness forvarious thicknesses of a silicon dioxide layer of the elastic wavedevice of FIG. 21.

FIG. 31A illustrates a relationship between Qs and 5LN thicknesses forvarious silicon dioxide layer thicknesses of the elastic wave device ofFIG. 21. FIG. 31B illustrates a relationship between Qp and 5LNthicknesses for various silicon dioxide layer thicknesses of the elasticwave device of FIG. 21.

FIGS. 32A and 32B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer. FIG. 32A corresponds to a 5LN with a thickness of 0.25λ.FIG. 32B corresponds to a 5LN with a thickness of 0.5λ.

FIGS. 33A to 33C illustrate spurious modes in frequency responses forvarious 5LN elastic wave devices. FIG. 33A relates to 5LN/Si elasticwave device with a LN layer that is 0.25λ thick. FIG. 33B relates to5LN/Si elastic wave device with a LN layer that is 1λ thick. FIG. 33Crelates to a 5LN/SiO₂/Si elastic wave device.

FIG. 34A is a contour plot for Vo for the elastic wave device of FIG.21. FIG. 34B is a contour plot for k² for the elastic wave device ofFIG. 21.

FIG. 35A is a contour plot for Qs for the elastic wave device of FIG.21. FIG. 35B is a contour plot for Qp for the elastic wave device ofFIG. 21.

FIG. 36A is a contour plot for Qavg for the elastic wave device of FIG.21. FIG. 36B is a contour plot for FOM for the elastic wave device ofFIG. 21.

FIGS. 37A to 37F are graphs that compare various parameters for elasticwave devices with a silicon dioxide layer in various positions. FIG. 37Ais a graph of Vo as a function of piezoelectric layer height. FIG. 37Bis a graph of k² as a function of piezoelectric layer height. FIG. 37Cis a graph of Qs as a function of piezoelectric layer height. FIG. 37Dis a graph of Qp as a function of piezoelectric layer height. FIG. 37Eis a graph of Qavg as a function of piezoelectric layer height. FIG. 37Fis a graph of FOM as a function of piezoelectric layer height.

FIG. 38A is graph of k² as a function of a cut angle of an LN layer inan elastic wave device of FIG. 21 that includes an LN piezoelectric on asilicon substrate with a silicon dioxide layer disposed therebetween.

FIG. 38B is graph of v_(P-OPEN) as a function of a cut angle of an LNlayer in an elastic wave device of FIG. 21 that includes an LNpiezoelectric on a silicon substrate with a silicon dioxide layerdisposed therebetween.

FIG. 38C is graph of Qs as a function of a cut angle of an LN layer inan elastic wave device of FIG. 21 that includes an LN piezoelectric on asilicon substrate with a silicon dioxide layer disposed therebetween.

FIG. 38D is graph of Qp as a function of a cut angle of an LN layer inan elastic wave device of FIG. 21 that includes an LN piezoelectric on asilicon substrate with a silicon dioxide layer disposed therebetween.

FIGS. 39A to 39L illustrate admittance over frequency for various cutangles of LN of an elastic wave device of FIG. 21 that includes an LNpiezoelectric on a silicon substrate with a silicon dioxide layerdisposed therebetween. FIG. 39A corresponds to a cut angle of −30°. FIG.39B corresponds to a cut angle of −20°. FIG. 39C corresponds to a cutangle of −10°. FIG. 39D corresponds to a cut angle of 0°. FIG. 39Ecorresponds to a cut angle of 10°. FIG. 39F corresponds to a cut angleof 20°. FIG. 39G corresponds to a cut angle of 30°. FIG. 39H correspondsto a cut angle of 40°. FIG. 39I corresponds to a cut angle of 50°. FIG.39J corresponds to a cut angle of 60°. FIG. 39K corresponds to a cutangle of 70°. FIG. 39L corresponds to a cut angle of 80°.

FIG. 40 is a cross-sectional view of an elastic wave device according toan embodiment.

FIGS. 41A and 41B are graphs of simulations of an elastic wave device ofFIG. 40 having a lithium niobate piezoelectric layer, a high velocitylayer, and a dielectric layer over the IDT electrode. FIG. 41A is agraph of k² as a function of LN thickness for various thicknesses of thedielectric layer. FIG. 41B is a graph of temperature coefficient ofvelocity (TCV) as a function of LN thickness for various thicknesses ofthe dielectric layer.

FIGS. 42A to 42D are graphs of simulations of an elastic wave device ofFIG. 40 that includes silicon dioxide over a LN piezoelectric layer on asilicon substrate. FIG. 42A corresponds to LN having a cut angle of 0°.FIG. 42B corresponds to LN having a cut angle of 10°. FIG. 42Ccorresponds to LN having a cut angle of 20°. FIG. 42D corresponds to LNhaving a cut angle of 30°.

FIGS. 43A and 43B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer for an elastic wave device of FIG. 40 with a 5LNpiezoelectric layer. FIG. 43A corresponds to a 5LN piezoelectric layerwith a thickness of 0.25λ. FIG. 43B corresponds to a 5LN piezoelectriclayer with a thickness of 0.5λ.

FIG. 44A is a graph of k² as a function of 5LN thickness for variousthicknesses of a silicon dioxide layer of an elastic wave device of FIG.40. FIG. 44B is a graph of v_(P-OPEN) as a function of 5LN thickness forvarious thicknesses of a silicon dioxide layer of an elastic wave deviceof FIG. 40.

FIG. 45A illustrates a relationship between Qs and 5LN thickness forvarious silicon dioxide layer thicknesses an elastic wave device of FIG.40. FIG. 45B illustrates a relationship between Qp and 5LN thicknessesfor various silicon dioxide layer thicknesses of an elastic wave deviceof FIG. 40.

FIGS. 46A and 46B illustrate relationships between (1) TCF and thicknessof a silicon dioxide layer and (2) k² and thickness of the silicondioxide layer for an elastic wave device of FIG. 40 with a 42LNpiezoelectric layer. FIG. 46A corresponds to a 42LT piezoelectric layerwith a thickness of 0.25λ. FIG. 46B corresponds to a 42LT piezoelectriclayer with a thickness of 0.5λ.

FIG. 47A is a graph of k² as a function of 42LT thickness for variousthicknesses of a silicon dioxide layer of an elastic wave device of FIG.40. FIG. 47B is a graph of v_(P-OPEN) as a function of 42LT thicknessfor various thicknesses of the silicon dioxide layer of an elastic wavedevice of FIG. 40.

FIG. 48A illustrates a relationship between Qs and 42LT thickness forvarious silicon dioxide layer thicknesses of an elastic wave device ofFIG. 40. FIG. 48B illustrates a relationship between Qp and 42LTthicknesses for various silicon dioxide layer thicknesses of an elasticwave device of FIG. 40.

FIG. 49A is graph of k² as a function of a cut angle of an LN layer inan elastic wave device of FIG. 40 that includes a silicon dioxide layerover an LN piezoelectric layer on a silicon substrate.

FIG. 49B is graph of v_(P-OPEN) as a function of a cut angle of an LNlayer in an elastic wave device of FIG. 40 that includes a silicondioxide layer over an LN piezoelectric layer on a silicon substrate.

FIG. 49C is graph of Qs as a function of a cut angle of an LN layer inan elastic wave device of FIG. 40 that includes a silicon dioxide layerover an LN piezoelectric layer on a silicon substrate.

FIG. 49D is graph of Qp as a function of a cut angle of an LN layer inan elastic wave device of FIG. 40 that includes a silicon dioxide layerover an LN piezoelectric layer on a silicon substrate.

FIGS. 50A to 50L illustrate admittance over frequency for various cutangle of LN in an elastic wave device of FIG. 40 that includes a silicondioxide layer over an LN piezoelectric layer on a silicon substrate.FIG. 50A corresponds to a cut angle of −30°. FIG. 50B corresponds to acut angle of −20°. FIG. 50C corresponds to a cut angle of −10°. FIG. 50Dcorresponds to a cut angle of 0°. FIG. 50E corresponds to a cut angle of10°. FIG. 50F corresponds to a cut angle of 20°. FIG. 50G corresponds toa cut angle of 30°. FIG. 50H corresponds to a cut angle of 40°. FIG. 50Icorresponds to a cut angle of 50°. FIG. 50J corresponds to a cut angleof 60°. FIG. 50K corresponds to a cut angle of 70°. FIG. 50L correspondsto a cut angle of 80°.

FIG. 51 is a plan view of the elastic wave device of FIG. 40.

FIG. 52 is a cross-sectional view of an elastic wave device according toanother embodiment.

FIG. 53A is a schematic diagram of a filter that includes an elasticwave device according to one or more embodiments.

FIG. 53B is a schematic diagram of another filter that includes anelastic wave device according to one or more embodiments.

FIG. 53C is a schematic diagram of another filter that includes anelastic wave device according to one or more embodiments.

FIG. 53D is a schematic diagram of another filter that includes anelastic wave device according to one or more embodiments.

FIG. 54A is a schematic diagram of a duplexer that includes an elasticwave device according to one or more embodiments.

FIG. 54B is a schematic diagram of another duplexer that includes anelastic wave device according to one or more embodiments.

FIG. 54C is a schematic diagram of another duplexer that includes anelastic wave device according to one or more embodiments.

FIG. 55 is a schematic block diagram of a module that includes a poweramplifier, a switch, and a filter that includes an elastic wave inaccordance with one or more embodiments.

FIG. 56 is a schematic block diagram of a module that includes a poweramplifier, switches, and a filter that includes an elastic wave inaccordance with one or more embodiments.

FIG. 57 is a schematic block diagram of a module that includes a poweramplifier, a switch, and a duplexer that includes an elastic wave inaccordance with one or more embodiments.

FIG. 58 is a schematic block diagram of a wireless communication devicethat includes a filter with an elastic wave device in accordance withone or more embodiments.

FIG. 59 is a schematic diagram of a radio frequency system that includesa filter with an elastic wave device in accordance with one or moreembodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Elastic wave devices that include lithium niobate (LiNbO₃) with arelatively low cut angle can have a relatively large electromechanicalcoupling coefficient (k²). Such devices can operate in a leaky surfaceacoustic wave mode in which shear horizontal (SH) waves leak into asubstrate under the lithium niobate layer at anti-resonance (fp). At ananti-resonance frequency, an oscillation amplitude can be approximatelyzero. This can cause the quality factor (Q) of such devices to berelatively low. Q can represent a ratio of stored power to dissipatedpower. Q can be frequency dependent. A quality factor at resonance (Qs)can be different than a quality factor at anti-resonance (Qp). With arelatively low Q, such elastic wave devices can be unsuitable forcertain filter applications. Any of the elastic wave devices discussedherein can implement a surface acoustic wave (SAW) resonator. Thus, aSAW resonator can be implemented in accordance with any suitableprinciples and advantages discussed herein.

Copper (Cu) electrodes and gratings can be used to lower a phasevelocity of a leaky surface acoustic wave to prevent leakage from apiezoelectric layer, such as a lithium niobate layer. This can create aless leaky SH wave. Using heavy electrodes has resulted in difficulty insufficiently reducing leakage from a piezoelectric layer and achieving aQ that is desirable for use in a filter. In addition, Rayleigh wavespurs can be relatively close to resonance in such approaches, which canbe undesirable.

Aspects of this disclosure relate to using a silicon (Si) substrate toprevent leakage from a piezoelectric layer of an elastic wave device atanti-resonance. A bulk velocity of the silicon substrate can besignificantly higher than a velocity of the SH wave, which can preventleakage from a piezoelectric layer of the elastic wave device. Thepiezoelectric layer, such as a lithium niobate layer, can have arelatively low acoustic impedance and the silicon substrate can have arelatively high acoustic impedance. A difference in acoustic impedanceof the piezoelectric layer and the silicon substrate can create aneffective reflection at an interface of the piezoelectric layer and thesilicon substrate to prevent the SH wave from leaking into the siliconsubstrate. This can cause the anti-resonant Q to be significantlyimproved. The piezoelectric layer can have a thickness that is less thata wavelength of the SH wave. This can cause the plate wave spurs to beaway from resonance of the SH wave main mode. A temperature compensatinglayer, such as a silicon dioxide (SiO₂) layer, can be included over aninterdigital transducer electrode of the elastic wave device and thepiezoelectric layer to improve a temperature coefficient of frequency(TCF) of the elastic wave device.

An aspect of this disclosure is an elastic wave device that includes apiezoelectric layer, an interdigital transducer electrode on thepiezoelectric layer, and a high velocity layer in physical contact withthe piezoelectric layer. The piezoelectric layer has a cut angle in acut angle range from −10° to 60°. The interdigital transducer electrodeis configured to generate an elastic wave having a wavelength of λ. Thepiezoelectric layer has a thickness in a thickness range from 0.35λ to0.8λ. The high velocity layer has a higher bulk velocity than a velocityof the elastic wave. The thickness of the piezoelectric layer cancontribute to increasing a Qp of the elastic wave device. The cut anglecan contribute to relatively high k², Qp, and Figure of Merit values ofthe elastic wave device.

Another aspect of this disclosure is an elastic wave device thatincludes a lithium niobate layer, an interdigital transducer electrodeon the lithium niobate layer, and a silicon substrate in physicalcontact with the lithium niobate layer. The lithium niobate layer has acut angle in a cut angle range from −10° to 60°. The interdigitaltransducer electrode is configured to generate an elastic wave having awavelength of λ. The lithium niobate layer has a thickness in athickness range from 0.35λ to 0.8λ. The thickness of the lithium niobatelayer can contribute to increasing a Qp of the elastic wave device. Thecut angle can contribute to relatively high k², Qp, and Figure of Meritvalues of the elastic wave device.

Another aspect of this disclosure is an elastic wave device thatincludes a lithium niobate layer, an interdigital transducer electrodeon the lithium niobate layer, a high velocity layer, and a temperaturecompensating layer. The lithium niobate layer has a cut angle in a cutangle range from −10° to 60°. The interdigital transducer electrode isconfigured to generate an elastic wave having a wavelength of λ. Thelithium niobate layer has a thickness in a thickness range from 0.35λ to0.8λ. The high velocity layer has a higher bulk velocity than a velocityof the surface acoustic wave. The high velocity layer is configured toprevent the surface acoustic wave from leaking from the lithium niobatelayer at anti-resonance. The temperature compensating layer is disposedbetween the high velocity layer and the lithium niobate layer. Thetemperature compensating layer has a positive temperature coefficient offrequency. The elastic device arranged so as to have anelectromechanical coupling coefficient of at least 26%.

Another aspect of this disclosure is an elastic wave device thatincludes a lithium tantalate layer, an interdigital transducer electrodeon the lithium tantalate layer, a high velocity layer, and a temperaturecompensating layer. The lithium tantalate layer has a cut angle in a cutangle range from −10° to 50°. The interdigital transducer electrode isconfigured to generate an elastic wave having a wavelength of λ. Thelithium tantalate layer has a thickness that is less than k. The highvelocity layer has a higher bulk velocity than a velocity of the surfaceacoustic wave. The high velocity layer is configured to prevent thesurface acoustic wave from leaking from the lithium niobate layer atanti-resonance. The temperature compensating layer is disposed betweenthe high velocity layer and the lithium tantalate layer. The temperaturecompensating layer has a positive temperature coefficient of frequency.

Another aspect of this disclosure is an elastic wave device thatincludes a piezoelectric layer, an interdigital transducer electrode onthe piezoelectric layer, and a high velocity layer. The piezoelectriclayer has a cut angle in a cut angle range from −10° to 60°. Theinterdigital transducer electrode is configured to generate an elasticwave having a wavelength of λ. The interdigital transducer electrode hasa thickness in a thickness range from 0.02λ to 0.1λ. The piezoelectriclayer has a thickness that is less than k. The high velocity layer has ahigher bulk velocity than a velocity of the elastic wave. The highvelocity layer is configured to prevent the elastic wave from leakingfrom the piezoelectric layer at anti-resonance. The thickness of theinterdigital transducer electrode can contribute to desirable k², Qp,and Figure of Merit values of the elastic wave device.

Another aspect of this disclosure is an elastic wave device thatincludes a piezoelectric layer, an interdigital transducer electrode onthe piezoelectric layer, a silicon layer configured to prevent theelastic wave from leaking from the piezoelectric layer atanti-resonance, and a temperature compensating layer having a positivetemperature coefficient of frequency. The piezoelectric layer has a cutangle in a cut angle range from −10° to 60°. The interdigital transducerelectrode is configured to generate an elastic wave having a wavelengthof λ. The piezoelectric layer has a thickness in a thickness range from0.25λ to 0.8λ. The piezoelectric layer is disposed between the siliconlayer and the interdigital transducer electrode. The interdigitaltransducer electrode being is disposed between the temperaturecompensating layer and the piezoelectric layer.

In certain embodiments, an elastic wave device including asub-wavelength thick lithium niobate layer having a relatively low cutangle on a silicon substrate can be effective at inhibiting and/orpreventing leakage of an SH wave and trapping energy on a surface of thelithium niobate layer on which an interdigital transducer (IDT)electrode is disposed. The relatively low cut angle can be in a rangefrom 20° to 30° in certain embodiments. In such elastic wave devices,the Q can be greater than about 2000 and the k² can be greater than 20%.Including a temperature compensating layer, such as silicon dioxide,over the interdigital transducer electrode can cause the TCF of theelastic wave device to be increased.

According to some embodiments, an elastic wave device includes a lithiumniobate layer that is bonded to a silicon substrate opposite to a sideof the lithium niobate layer on which an IDT electrode is disposed. Insuch embodiments, a relatively high anti-resonant Q (e.g., ananti-resonant Q of 2000 or greater) can be achieved by a lithium niobatelayer having a thickness that is less than a wavelength of an elasticwave of the elastic wave device and the silicon substrate. At the sametime, a relatively large k² (e.g., 20% or greater) can be achieved byhaving a relatively low cut angle (e.g., a cut angle in a range from 20°to 30°).

In some other embodiments, an elastic wave device can include adielectric layer (e.g., a silicon dioxide layer) that is disposedbetween a sub-wavelength thick lithium niobate layer having a relativelylow cut angle and a silicon substrate. The dielectric layer can bringthe TCF closer to zero. Accordingly, frequency dependence on lithiumniobate thickness can be reduced.

FIG. 1 is a cross-sectional view of an elastic wave device 10 accordingto an embodiment. As illustrated, the elastic wave device 10 includes apiezoelectric layer 12, an IDT electrode 14, and a high velocity layer16.

The piezoelectric layer 12 can be a lithium niobate (LiNbO₃) layer or alithium tantalate (LiTaO₃) layer, for example. The illustratedpiezoelectric layer 12 has a thickness H₁ that is less that a wavelengthof an elastic wave generated by the IDT electrode 14 of the elastic wavedevice 10. The piezoelectric layer 12 can have a relatively low cutangle. For instance, the cut angle of the piezoelectric layer 12 can bea range from −10° to 35°. In some embodiments, the cut angle of thepiezoelectric layer can be in a range from 15° to 35° or a range from20° to 30°. As used herein, a “cut angle” of N^(o) refers to an N^(o)rotated Y-cut in a Y-cut X-propagation piezoelectric layer. Accordingly,for a piezoelectric layer with Euler angles (φ, θ, ψ), the “cut angle”in degrees can be θ minus 90°.

An IDT electrode 14 is disposed on piezoelectric layer 12. The IDTelectrode 14 can generate an elastic wave on a surface of thepiezoelectric layer 12. The illustrated IDT electrode 14 has a pitch L₁and a thickness h. The pitch L₁ is the wavelength λ of an elastic wavegenerated by the elastic wave device 10. The IDT electrode 14 caninclude aluminum and/or any other suitable material for an IDT electrode14. For example, IDT electrode material can include aluminum (Al),titanium (Ti), gold (Au), silver (Ag), copper (Cu), platinum (Pt),tungsten (W), molybdenum (Mo), ruthenium (Ru), or any suitablecombination thereof. In certain applications, the IDT electrode 14 caninclude aluminum. For instance, the IDT electrode can include analuminum alloy, such as aluminum and copper.

In the illustrated elastic wave device 10, the high velocity layer 16 isbonded to and in physical contact with the piezoelectric layer 12. Thehigh velocity layer 16 has a higher bulk velocity than a velocity of theelastic wave generated by the IDT electrode 14. The high velocity layer16 can have a higher acoustic impedance than piezoelectric layer 12. Thehigh velocity layer 16 can inhibit an elastic wave generated by theelastic wave device 10 from leaking from the piezoelectric layer 12 atanti-resonance. The high velocity layer 16 can be a silicon layer. Sucha silicon layer can have a relatively high acoustic velocity, arelatively large stiffness, and a relatively small density. The siliconlayer can be a polycrystalline silicon layer in certain instances.

In some instances, the elastic wave device 10 includes a lithiumtantalate piezoelectric layer bonded with a silicon substrate. FIGS. 2Ato 4E illustrate simulation results associated with such elastic wavedevices.

FIGS. 2A to 2E are graphs of simulations of an elastic wave device 10with a lithium tantalate piezoelectric layer having a cut angle of 42°,a high velocity layer that is a silicon substrate, and an IDT electrodehaving a pitch L₁ of 2.0 um and a thickness h of 160 nm. The pitch L₁ isthe wavelength λ of the elastic wave. Thus, the thickness h of 160 nmcorresponds to 0.08λ. The thickness H₁ of the lithium tantalate layerwas swept in this elastic wave device. FIG. 2A is a graph that shows thefrequency responses for thickness H₁ of a lithium tantalate layer thatare 0.25λ and 0.5λ and for a corresponding device without a siliconsubstrate, where λ is the wavelength of an elastic wave generated by theIDT electrode. The wavelength λ is represented by “L” in some figures.FIG. 2B shows that a maximum k² for the device is achieved when thethickness of the lithium tantalate layer is around 0.25λ. FIG. 2Cillustrates that Qs can increase with when the thickness H₁ of thelithium tantalate layer is lower. FIG. 2D illustrates that a figure ofmerit (FOM) has a high value for a range of thickness H₁ of the lithiumtantalate layer from about 0.2λ to 0.3λ. FIG. 2E illustrates that Vssensitivity can increase with a thinner lithium tantalate layer.

FIGS. 3A to 3E are graphs of simulations of an elastic wave device 10with a lithium tantalate piezoelectric layer having a cut angle of 42°and a thickness H₁ of 0.25λ (where λ is the wavelength of the elasticwave), a high velocity layer that is a silicon substrate, and an IDTelectrode having a pitch L₁ of 2.0 um. The thickness h of the IDTelectrode was swept in this elastic wave device. FIG. 3A is a graph thatshows the frequency responses for thickness h of an IDT electrode thatare 0.08λ and 0.16λ and for a corresponding device without the siliconsubstrate bonded with the lithium tantalate layer. FIG. 3B shows that k²for the device can start to decrease when h is less than about 0.08λ.FIG. 3C illustrates that Qs and Qp can increase with greater IDTelectrode thickness h. FIG. 3D illustrates that FOM can increase withgreater IDT electrode thickness h. FIG. 3E illustrates that Vssensitivity can increase with a thinner IDT electrode.

FIGS. 4A to 4E are graphs of simulations of an elastic wave device 10with a lithium tantalate piezoelectric layer having a thickness H₁ of0.25λ (where λ is the wavelength of the elastic wave), a high velocitylayer that is a silicon substrate, and an IDT electrode having a pitchL₁ of 2.0 um and a height h of 0.08λ. The cut angle of the lithiumtantalate layer was swept in this elastic wave device. FIG. 4A is agraph that shows the frequency responses for cut angles of 42° and 120°and for a corresponding device without the silicon substrate bonded withthe lithium tantalate layer. FIG. 4B shows that k² for the device can beat a maximum for a cut angle of about 20°. FIG. 4C illustrates Qs and Qpversus cut angle. FIG. 4D illustrates that FOM can have a maximum for acut angle of around 20° to 30°. FIG. 4E illustrates Vs versus cut angle.

In certain instances, the elastic wave device 10 includes a lithiumniobate piezoelectric layer bonded with a silicon substrate. FIGS. 5A to7E illustrate simulation results associated with such elastic wavedevices.

FIGS. 5A to 5E are graphs of simulations of an elastic wave device 10with a lithium niobate piezoelectric layer having a cut angle of 42°, ahigh velocity layer that is a silicon substrate, and an IDT electrodehaving a pitch L₁ of 2.0 um and a thickness h of 160 nm or 0.08λ. Thethickness H₁ of the lithium niobate layer was swept in this elastic wavedevice. FIG. 5A is a graph that shows the frequency responses forthickness H₁ of a lithium niobate layer that are 0.25λ and 0.5λ (where λis the wavelength of an elastic wave generated by the IDT electrode) andfor a corresponding device without a silicon substrate. FIG. 5B showsthat a maximum k² for the device can be achieved when the thickness ofthe lithium niobate layer that is around 0.25λ. FIG. 5C illustrates thatQs can increase with when the thickness H₁ of the lithium niobate layeris lower. FIG. 5D illustrates that a figure of merit (FOM) has arelatively high value for a range of thickness H₁ of the lithium niobatelayer from about 0.2λ to 0.4λ. FIG. 5E illustrates that Vs sensitivitycan increase with a thinner lithium niobate layer.

FIGS. 6A to 6E are graphs of simulations of an elastic wave device 10with a lithium niobate piezoelectric layer having a cut angle of 42° anda thickness H₁ of 0.25λ (where λ is the wavelength of the elastic wave),a high velocity layer that is a silicon substrate, and an IDT electrodehaving a pitch L₁ of 2.0 um. The thickness h of the IDT electrode wasswept in this elastic wave device. FIG. 6A is a graph that shows thefrequency responses for thickness h of an IDT electrode that are 0.08λand 0.12λ and for a corresponding device without the silicon substratebonded with the lithium niobate layer. FIG. 6B shows that k² for thedevice can decrease for thicker IDT electrodes. FIG. 6C illustrates thatQs and Qp can increase with greater IDT electrode thickness h. FIG. 6Dillustrates that FOM can increases with greater IDT electrode thicknessh. FIG. 6E illustrates that Vs sensitivity can increase with a thinnerIDT electrode. FIGS. 6B to 6E show that an elastic wave device can havedesirable characteristics when the IDT electrode has a thickness in arange from 0.02λ to 0.1λ.

FIGS. 7A to 7E are graphs of simulations of an elastic wave device 10with a lithium niobate piezoelectric layer having a thickness H₁ of0.25λ (where λ is the wavelength of the elastic wave), a high velocitylayer that is a silicon substrate, and an IDT electrode having a pitchL₁ of 2.0 um and a height h of 0.08λ. The cut angle of the lithiumniobate layer was swept in this elastic wave device. FIG. 7A is a graphthat shows the frequency responses for cut angles of 42° and 128° andfor a corresponding device without the silicon substrate bonded with thelithium niobate layer. FIG. 7B shows that k² for the device can be at amaximum for a cut angle of about 20°. FIG. 7C illustrates Qs and Qpversus cut angle. FIG. 7D illustrates that FOM can have a maximum for acut angle of around 20° to 30°. FIG. 7E illustrates Vs versus cut angle.

FIGS. 8A to 8F compare simulation results for an elastic wave device 10that has a lithium tantalate (LT) piezoelectric layer with elastic wavedevice 10 that has a lithium niobate (LN) piezoelectric layer. In thesefigures and some other figures, “L” represents the wavelength λ of theelastic wave. FIG. 8A shows that an elastic wave device with an LNpiezoelectric layer can have a higher k² than an elastic wave devicewith an LT piezoelectric layer for various piezoelectric layerthicknesses. FIG. 8B shows that an elastic wave device with an LNpiezoelectric layer can have a higher k² than an elastic wave devicewith an LT piezoelectric layer for various IDT electrode thicknesses.FIG. 8C shows that an elastic wave device with an LN piezoelectric layercan have a higher k² than an elastic wave device with an LTpiezoelectric layer for various cut angles. FIG. 8D shows that anelastic wave device with an LN piezoelectric layer can have a higher FOMthan an elastic wave device with an LT piezoelectric layer for variouspiezoelectric layer thicknesses. FIG. 8E shows that an elastic wavedevice with an LN piezoelectric layer can have a higher FOM than anelastic wave device with an LT piezoelectric layer for various IDTelectrode thicknesses. FIG. 8F shows that an elastic wave device with anLN piezoelectric layer can have a higher FOM than an elastic wave devicewith an LT piezoelectric layer for various cut angles.

FIG. 9 is a graph of phase velocity (Vp) versus piezoelectric layerthickness for an elastic wave device 10 with an LT piezoelectric layerwith a 42° cut angle and silicon substrate as a high velocity layer. Asused herein, 42LT can refer to lithium tantalate with a 42° cut angle.Phase velocity (Vp) of the elastic wave device can be modeled by thefollowing equations:

v _(p,m) ≈f _(s) xλ  (Equation 1)

v _(p,o) ≈f _(s) xλ  (Equation 2)

An SH wave can get reflected back to the LT layer at the LT/Si interfaceand concentrate on the surface of the LT layer when v_(SH),42LT/Si<v_(L), Si. An SH wave can be coupled with bulk mode and leakinto the substrate for (leaky SAW) for an elastic wave device with justa 42LT layer with an IDT electrode.

FIG. 10 is a graph of k² versus piezoelectric layer thickness for anelastic wave device 10 with an LT piezoelectric layer with a 42° cutangle and silicon substrate as a high velocity layer. K² can be modeledby the following equation:

$\begin{matrix}{k^{2} = {\frac{\pi}{2}{\frac{fs}{fp}/{\tan \left( {\frac{\pi}{2}\frac{fs}{fp}} \right)}}}} & \left( {{Equation}\mspace{14mu} 3} \right)\end{matrix}$

In this simulation, a maximum k² of about 10% is achieved at an LT layerthickness of about 0.25λ. Lamb modes can be present in a pass band atcertain thicknesses of the LT layer.

FIG. 11A is a graph of the quality factor versus piezoelectric layerthickness for an elastic wave device 10 with an LT piezoelectric layerwith a 42° cut angle and silicon substrate as a high velocity layer. Qpis boosted in such an elastic wave device related to a substrate thatconsists only of 42LN instead of 42LN/Si. FIG. 11B illustrates thatwaves can be trapped on the surface of an elastic wave device 10 with anLT piezoelectric layer with a 42° cut angle and silicon substrate as ahigh velocity layer. This can correspond to an increase in Qp. Bycontrast, FIG. 11C illustrates that elastic waves can leak into thesubstrate for a similar elastic wave device that does not include asilicon substrate. With a 42LT substrate and no silicon substrate, Qscan be 1846 and Qp can be 1406 in some instances. Accordingly, FIG. 11Aillustrates that a silicon substrate bonded with a LT layer can causethe Qp of an elastic wave device to be significantly increased.

FIGS. 12A to 12D illustrates spurious modes for an elastic wave device10 with an LT piezoelectric layer and silicon substrate as a highvelocity layer for various thicknesses of the LT layer. FIG. 12Acorresponds to LT thickness of 0.05λ, FIG. 12B corresponds to LTthickness of 0.75λ, FIG. 12C corresponds to LT thickness of 0.25λ, andFIG. 12D corresponds to LT thickness of 1λ.

In an elastic wave device 10 with an LT piezoelectric layer with a 42°cut angle and silicon substrate as a high velocity layer, a temperaturecoefficient of frequency (TCF) does not appear to change significantlyas thickness of the LT layer changes. TCF does not appear to be impactedsignificantly by the silicon substrate.

FIGS. 13A to 13C illustrates an impact of the thickness of an aluminumIDT electrode on an elastic wave device 10 with an LT piezoelectriclayer with a thickness of 0.25λ and silicon substrate as a high velocitylayer for various thicknesses of the LT layer. FIG. 13A illustrates animpact of IDT electrode thickness on Q. FIG. 13B illustrates an impactof IDT electrode thickness on Vp. FIG. 13C illustrates an impact of IDTelectrode thickness on k².

While several of the simulations discussed above are based on a 2 GHzdevice, similar results are expected for Vp, k², and Q for elastic wavedevices arranged to generate elastic waves having different frequencies.Thus, results have been presented in terms of wavelength k. Forinstance, an elastic wave device arranged to generate an elastic wavewith a wavelength of 2 um and a frequency of about 2 GHz can havesimilar properties as a corresponding elastic wave device with arrangedto generate an elastic wave of with a wavelength of 4 um and a frequencyof about 1 GHz.

FIG. 14A illustrates normalized average surface displacement atanti-resonance (fp) for an elastic wave device with a lithium niobate(LN) substrate with a thickness of 0.5λ and a cut angle of 5°. Such adevice can experience leakage into the LN substrate as shown in FIG.14A. FIG. 14B illustrates normalized average surface displacement at fpfor an elastic wave device 10 with a lithium niobate (LN) substrate witha thickness of 0.5λ and a cut angle of 5° and a silicon substrate forthe high velocity layer. Such a device can have elastic waves trapped ata surface of the LN layer as indicated by FIG. 14B.

FIGS. 15A to 15D are graphs for simulations of an elastic wave device 10with an LN piezoelectric layer and a silicon substrate as a highvelocity layer that show relationships between thickness of the LN layerand various parameters. FIG. 15A illustrates k² as a function ofthickness of the LN layer. FIG. 15B illustrates Qp versus thickness ofthe LN layer. FIG. 15B illustrates relatively high Qp values for LNthicknesses in a range from 0.35λ to 0.8λ. The electromechanicalcoupling coefficient k² is also relatively high for LN thicknesses in arange from 0.35λ to 0.8λ. FIG. 15C illustrates Qs versus thickness ofthe LN layer. FIG. 15D illustrates v₀ versus thickness of the LN layer.

FIGS. 16A to 16K illustrate admittance over frequency for an elasticwave device 10 with an LN piezoelectric layer having a thickness of 0.5λand a silicon substrate as a high velocity layer for various cut anglesof LN. As shown in FIGS. 16A to 16E, Rayleigh spurious responses can bepresent for cut angles of −30°, −20°, −10°, 0°, and 10°. As shown inFIGS. 16H to 16K, S₀ Lamb spurious responses can be present for cutangles of 40°, 50°, 60°, and 70°. The frequency responses for cut anglesof 20° and 30° shown in FIGS. 16F and 16G do not include significantRayleigh spurious responses or S₀ Lamb spurious responses. Accordingly,a cut angle in a range from about 15° to 35° can be advantageous.

FIG. 17A is a graph for simulations of an elastic wave device 10 with asilicon substrate as a high velocity layer that shows relationshipsbetween thickness of the LN or LT piezoelectric layer and k² for certaincut angles. FIG. 17A shows that k² can be significantly higher for an LNpiezoelectric layer with a cut angle of 5° compared to an LTpiezoelectric layer with cut angle of 42° or an LN piezoelectric layerwith a cut angle of 128°.

FIG. 17B is a graph for simulations of an elastic wave device 10 with asilicon substrate as a high velocity layer that shows relationshipsbetween thickness of the LN or LT piezoelectric layer and v₀ for certaincut angles. FIG. 17B shows that v₀ can be higher for an LN piezoelectriclayer with a cut angle of 5° compared to an LT piezoelectric layer withcut angle of 42° or an LN piezoelectric layer with a cut angle of 128°.

FIG. 18A to 18C are graphs for simulations of an elastic wave device 10with an LN piezoelectric layer having a 128° cut angle and a siliconsubstrate as a high velocity layer. FIG. 18A illustrates a frequencyresponse for a LN layer having a thickness of 0.7λ. FIG. 18B illustratesa frequency response for a LN layer having a thickness of 1λ. FIG. 18Cillustrates a frequency response for a LN layer having a theoreticallyinfinite thickness.

FIG. 19 illustrates relationships between velocity of the elastic wavedevice 10 and thickness of the piezoelectric layer.

FIGS. 20A and 20B are graphs for simulations of Q as a function ofthickness of the piezoelectric layer of an elastic wave device 10 forcertain piezoelectric layers, in which a silicon substrate is the highvelocity layer. FIG. 20A is a graph of Qs as a function of thickness ofcertain piezoelectric layers. FIG. 20B is a graph of Qp as a function ofthickness of certain piezoelectric layers. The dots on FIGS. 20A and 20Brepresent Qs and Qp values, respectively, for elastic wave devices thatare similar except they do not include a silicon substrate.

FIG. 21 is a cross-sectional view of an elastic wave device 20 accordingto an embodiment. As illustrated, the elastic wave device 20 includes apiezoelectric layer 12, an IDT electrode 14, and a high velocity layer16, and a temperature compensating layer 22. The elastic wave device 20is like the elastic wave device 10 of FIG. 1 except that a temperaturecompensating layer 22 is disposed between the piezoelectric layer 12 andthe high velocity layer 16. As illustrated, the temperature compensatinglayer 22 has a first side in physical contact with the piezoelectriclayer 12 and a second side in physical contact with the high velocitylayer 16. The temperature compensating layer 22 can improve the TCF ofthe elastic wave device 20 relative to the elastic wave device 10.

The temperature compensating layer 22 can bring the TFC of the elasticwave device 20 closer to zero than the TCF of a similar elastic wavedevice that does not include the temperature compensating layer. Thetemperature compensating layer 22 can have a positive temperaturecoefficient of frequency. For instance, the temperature compensatinglayer 22 can be a silicon dioxide (SiO₂) layer. The temperaturecompensating layer 22 can alternatively be a tellurium dioxide (TeO₂)layer or a SiOF layer. The temperature compensating layer 22 can includeany suitable combination of SiO₂, TeO₂, and/or SiOF. The temperaturecompensating layer 22 can have a lower bulk velocity than a velocity ofthe elastic wave generated by the IDT electrode 14. The temperaturecompensating layer 22 can be a dielectric layer. The temperaturecompensating layer 22 can have a lower acoustic impedance than thepiezoelectric layer 12. The temperature compensating layer 22 can have alower acoustic impedance than the high velocity layer 16. Theillustrated temperature compensating layer 22 has a thickness H₂.

The elastic wave device 20 of FIG. 21 can have a higher quality factorthan an elastic wave device that consists of an IDT electrode on a piezoelectric layer. For instance, an elastic wave device 20 with an LT or LNpiezoelectric layer on silicon dioxide on silicon can have a qualityfactor in a range from about 2000 to 5000. As an example, an elasticwave device 20 can have a quality factor of about 3000 and acorresponding elastic wave device that consists of an IDT electrode on apiezoelectric layer can have a quality factor of about 1000. The qualityfactor may be process dependent.

FIGS. 22A to 28B are graphs of simulations of an elastic wave device 20having a lithium tantalate piezoelectric layer with a 42° cut angle(42LT), a high velocity layer that is a silicon substrate, and atemperature compensating layer that is a silicon dioxide layer.

FIG. 22A is a graph of k² as a function of 42LT thickness for variousthicknesses of the silicon dioxide layer. A maximum k² of about 12.5% inthis graph corresponds to a 42LT thickness of about 0.15λ and a silicondioxide thickness of 0.2λ.

FIG. 22B is a graph of v_(P-OPEN) as a function of 42LT thickness forvarious thicknesses of the silicon dioxide layer. FIG. 22B indicatesthat Vp dispersion is almost flat for a silicon dioxide thickness ofabout 0.05λ to 0.1λ.

FIG. 23A illustrates a relationship between Qs and 42LT thicknesses forvarious silicon dioxide layer thicknesses. A maximum Qs of about 1865 inthis graph corresponds to a 42LT thickness of about 0.7λ and a silicondioxide thickness of about 0.5λ. FIG. 23B illustrates a relationshipbetween Qp and 42LT thicknesses for various silicon dioxide layerthicknesses. A maximum Qp of about 2015 in this graph corresponds to a42LT thickness of about 0.65λ and a silicon dioxide thickness of about0.25λ. The dots in FIGS. 23A and 23B indicate that a similar elasticwave device without the silicon substrate and the silicon dioxide layerhas Qs of 1846 and Qp of 1406, respectively. Accordingly, the siliconsubstrate and the silicon dioxide layer can improve Qs and Qp. Asindicated by these graphs, Qp can be improved more than Qs by thesilicon substrate and the silicon dioxide layer.

FIGS. 24A and 24B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer. FIG. 24A corresponds to 42LT with a thickness of 0.25λ.An average TCF of 0 occurs at a silicon dioxide thickness of about 0.7λin FIG. 24A. FIG. 24B corresponds to 42LT with a thickness of 0.5λ. Anaverage TCF of 0 occurs at a silicon dioxide thickness of about 0.9λ inFIG. 24B.

FIGS. 25A to 25C illustrate spurious modes in frequency responses forvarious 42LT and silicon dioxide thicknesses. FIG. 25A shows arelatively clean frequency response for a 42LT layer with a thickness of0.15λ and a silicon dioxide thickness of 0.2λ. FIG. 25B shows a Rayleighwave in a pass band when the 42LT layer has a thickness of less than0.03λ. FIG. 25C shows a plate wave in a pass band when the 42LT layerhas a thickness of greater than 0.8λ. The passband can be relativelyclean when the 42LT layer has a thickness in a range from about 0.03λ to0.8λ.

FIG. 26A is a contour plot for Vo. FIG. 26B is a contour plot for k².FIG. 26B indicates a maximum k² of about 12.5% for a 42LT thickness ofabout 0.15λ and a silicon dioxide thickness of about 0.2λ.

FIG. 27A is a contour plot for Qs. FIG. 27A indicates a maximum Qs ofabout 1865 for a 42LT thickness of about 0.7λ and a silicon dioxidethickness of about 0.5λ. FIG. 27B is a contour plot for Qp. FIG. 27Bindicates a maximum Qp of about 2015 for a 42LT thickness of about 0.65λand a silicon dioxide thickness of about 0.25λ.

FIG. 28A is a contour plot for Qavg. Qavg can be an average of Qp andQs. FIG. 28A indicates a maximum Qavg of about 1935 for a 42LT thicknessof about 0.65λ and a silicon dioxide thickness of about 0.3λ. FIG. 28Bis a contour plot for FOM. FIG. 28B indicates a maximum FOM of about 225for a 42LT thickness of about 0.175λ and a silicon dioxide thickness ofabout 0.2λ.

In the elastic wave device 20 of FIG. 21, Qp can be boosted relative toa similar elastic wave device without the temperature compensating layerand the high velocity layer. This can be due to displacement beingconfined to the surface of the piezoelectric layer 12 of the elasticwave device 20. FIGS. 29A to 29D illustrate displacement being confinedto the surface of the piezoelectric layer for 42LT and 5LN piezoelectriclayers in the elastic wave device 20 while displacement is not asconfined to the surface in similar elastic wave devices without a highvelocity layer and a temperature compensating layer.

FIGS. 30A to 36B are graphs of simulations of an elastic wave device 20having a lithium niobate piezoelectric layer with a 5° cut angle (5LN),a high velocity layer that is a silicon substrate, and a temperaturecompensating layer that is a silicon dioxide layer.

FIG. 30A is a graph of k² as a function of 5LN thickness for variousthicknesses of the silicon dioxide layer. A maximum k² of about 29.5% inthis graph corresponds to a 5LN thickness of about 0.5λ and a silicondioxide thickness of 0.05λ.

FIG. 30B is a graph of v_(P-OPEN) as a function of 5LN thickness forvarious thicknesses of the silicon dioxide layer.

FIG. 31A illustrates a relationship between Qs and 5LN thicknesses forvarious silicon dioxide layer thicknesses. A maximum Qs of about 1815 inthis graph corresponds to a 5LN thickness of about 0.7λ and a silicondioxide thickness of about 0.9λ. FIG. 31B illustrates a relationshipbetween Qp and 5LN thicknesses for various silicon dioxide layerthicknesses. A maximum Qp of about 2460 in this graph corresponds to a5LN thickness of about 0.55λ and a silicon dioxide thickness of about0.2λ. The dots in FIGS. 31A and 31B indicate that a similar elastic wavedevice without the silicon substrate and the silicon dioxide layer hasQs of 1798 and Qp of 40.5, respectively. Accordingly, the siliconsubstrate and the silicon dioxide layer can boost Qp significantly inthe elastic wave device 20 with a 5LN piezoelectric layer.

FIGS. 32A and 32B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer. FIG. 32A corresponds to a 5LN with a thickness of 0.25λ.FIG. 32B corresponds to a 5LN with a thickness of 0.5λ.

FIGS. 33A to 33C illustrate spurious modes in frequency responses forvarious 5LN elastic wave devices. FIGS. 33A and 33B relate to 5LN/Sielastic wave devices. FIG. 33C relates to a 5LN/SiO₂/Si elastic wavedevice. FIG. 33A shows a Rayleigh wave in a pass band when the 5LN layerhas a thickness of less than 0.3λ. FIG. 33B shows a plate mode responsein a pass band when the 5LN layer has a thickness of greater than 0.9λ.FIG. 33C shows a relatively clean frequency response for a 5LN layerwith a thickness of 0.5λ and a silicon dioxide layer with a thickness of0.05λ. A relatively clean passband can be achieved with a 5LN layer witha thickness in a range from about 0.3λ to 0.8λ.

FIG. 34A is a contour plot for Vo. FIG. 34B is a contour plot for k².FIG. 34B indicates a maximum k² of about 29.5% for a 5LN thickness ofabout 0.5λ and a silicon dioxide thickness of about 0.05λ.

FIG. 35A is a contour plot for Qs. FIG. 35A indicates a maximum Qs ofabout 1815 for a 5LN thickness of about 0.7λ and a silicon dioxidethickness of about 0.9λ. FIG. 35B is a contour plot for Qp. FIG. 35Bindicates a maximum Qp of about 2460 for a 5LN thickness of about 0.55λand a silicon dioxide thickness of about 0.2λ.

FIG. 36A is a contour plot for Qavg. FIG. 36A indicates a maximum Qavgof about 2130 for a 5LN thickness of about 0.6λ and a silicon dioxidethickness of about 0.26λ. FIG. 36B is a contour plot for FOM. FIG. 36Bindicates a maximum FOM of about 625 for a 5LN thickness of about 0.55λand a silicon dioxide thickness of about 0.1λ.

FIGS. 37A to 37F are graphs that compare various parameters for elasticwave devices with a silicon dioxide layer in various positions. Thesegraphs each include curves that correspond to elastic wave devices with(1) an aluminum IDT electrode over a 5LN piezoelectric layer over asilicon substrate, (2) an aluminum IDT electrode over a 5LNpiezoelectric layer over a silicon dioxide layer over a siliconsubstrate, (3) a silicon dioxide layer over an aluminum IDT electrodeover a 5LN piezoelectric layer over a silicon substrate, and (4) analuminum IDT electrode over a silicon dioxide layer over a 5LNpiezoelectric layer over a silicon substrate. These simulations sweepthickness of the 5LN piezoelectric layer and set the thickness of thesilicon dioxide layer at 0.1λ.

FIG. 37A is a graph of Vo. This graph indicates that low-velocitysilicon dioxide is least involved in wave propagation. FIG. 37B is agraph of k². FIG. 37B indicates that k² is particularly low when asilicon dioxide layer is disposed between an IDT electrode and a 5LNlayer. FIG. 37C is a graph of Qs. FIG. 37D is a graph of Qp. FIG. 37Dindicates that the Al/5LN/SiO₂/Si elastic wave has the best Qp. This canbe due to the largest reflection on the SiO₂/Si interface to preventleakage into the silicon substrate. FIG. 37E is a graph of Qavg. FIG.37F is a graph of FOM. These graphs indicate that SiO₂/Al/5LN/Si can beused as an alternative to 5LN/SiO2/Si, with slightly lower k² and Q.

FIG. 38A is graph of k² as a function of a cut angle of an LN layer inan elastic wave device 20 that includes an LN piezoelectric layer havinga thickness of 0.5λ, a high velocity layer that is a silicon substrate,and a temperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 38A indicates a maximum k² of about 30% at a cutangle of 10° and a silicon dioxide thickness of 0.

FIG. 38B is graph of v_(P-OPEN) as a function of a cut angle of an LNlayer in an elastic wave device 20 that includes an LN having athickness of 0.5λ, a high velocity layer that is a silicon substrate,and a temperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 38B indicates a maximum v₀ of about 4420 m/s ata cut angle of 35° and a silicon dioxide thickness of 0.

FIG. 38C is graph of Qs as a function of a cut angle of an LN layer inan elastic wave device 20 that includes an LN having a thickness of0.5λ, a high velocity layer that is a silicon substrate, and atemperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 38C indicates a maximum Qs of about 2135 at acut angle of 55° and a silicon dioxide thickness of 0.3λ.

FIG. 38D is graph of Qp as a function of a cut angle of an LN layer inan elastic wave device 20 that includes an LN having a thickness of0.5λ, a high velocity layer that is a silicon substrate, and atemperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 38D indicates a maximum Qp of about 2560 at acut angle of 25° and a silicon dioxide thickness of 0.25λ.

FIGS. 39A to 39L illustrate admittance over frequency for an elasticwave device 20 with an LN piezoelectric layer having a thickness of0.5λ, temperature compensating layer that is a silicon dioxide layerhaving a thickness of 0.1λ, and a high velocity layer that is a siliconsubstrate for various cut angles of LN.

FIG. 40 is a cross-sectional view of an elastic wave device 30 accordingto an embodiment. As illustrated, the elastic wave device 30 includes apiezoelectric layer 12, an IDT electrode 14, a high velocity layer 16,and a temperature compensating layer 32. The elastic wave device 30 islike the elastic wave device 10 of FIG. 1 except that a temperaturecompensating layer 32 is included over the IDT electrode 14 such thatthe IDT electrode 14 is between the piezoelectric layer 12 and thetemperature compensating layer 32. As illustrated, the temperaturecompensating layer 32 covers the IDT electrode 14 opposite thepiezoelectric layer 12. The temperature compensating layer 32 canimprove the TCF of the elastic wave device 30 relative to the elasticwave device 10.

The temperature compensating layer 32 can bring the TFC of the elasticwave device 30 closer to zero than the TCF of a similar elastic wavedevice that does not include the temperature compensating layer. Thetemperature compensating layer 32 can have a positive temperaturecoefficient of frequency. For instance, the temperature compensatinglayer 32 can be a silicon dioxide (SiO₂) layer. The temperaturecompensating layer 32 can alternatively be a tellurium dioxide (TeO₂)layer or a SiOF layer. The temperature compensating layer 32 can includeany suitable combination of SiO₂, TeO₂, and/or SiOF. The temperaturecompensating layer 32 can have a lower bulk velocity than a velocity ofthe elastic wave generated by the IDT electrode 14. The temperaturecompensating layer 32 can be a dielectric layer. The temperaturecompensating layer 32 can have a lower acoustic impedance than thepiezoelectric layer 12. The temperature compensating layer 32 can have alower acoustic impedance than the high velocity layer 16. Theillustrated temperature compensating layer 32 has a thickness H₃.

FIGS. 41A and 41B are graphs of simulations of an elastic wave device 30having a lithium niobate piezoelectric layer, a high velocity layer, anda temperature compensating layer over the IDT electrode. FIG. 41A is agraph of k² as a function of LN thickness for various thicknesses of thedielectric layer. FIG. 41B is a graph of temperature coefficient ofvelocity (TCV) as a function of LN thickness for various thicknesses ofthe temperature compensating layer.

FIGS. 42A to 42D are graphs of simulations of an elastic wave device 30configured to generate an elastic wave having a wavelength of 2.0 um, inwhich the elastic wave device 30 includes a high velocity layer that isa silicon substrate, an IDT electrode having a height of 160 nm (0.08λ),an SiO₂ temperature compensating layer with a thickness of 0.4 um (0.2λ)over the IDT electrode, and a lithium niobate piezoelectric layer with athickness of 0.5 um (0.25λ). FIGS. 42A to 42D correspond to differentcut angles of the lithium niobate piezoelectric layer. In particular,FIG. 42A corresponds to a cut angle of 0°, FIG. 42B corresponds to a cutangle of 10°, FIG. 42C corresponds to a cut angle of 20°, and FIG. 42Dcorresponds to a cut angle of 30°. As shown in FIG. 42C, a Rayleigh spurcan be suppressed for a cut angle of 20°. A cut angle in a range fromabout 15° to 25° can be desirable in an elastic wave device 30 with a LNpiezoelectric layer on a silicon substrate.

FIGS. 43A to 45B are graphs of simulations of an elastic wave device 30having a lithium niobate piezoelectric layer with a 5° cut angle (5LN),a high velocity layer that is a silicon substrate, and a temperaturecompensating layer that is a silicon dioxide layer.

FIGS. 43A and 43B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer. FIG. 43A corresponds to a 5LN piezoelectric layer with athickness of 0.25λ. An average TCF of 0 is indicated at a silicondioxide thickness of about 0.3λ in FIG. 43A. FIG. 43B corresponds to a5LN piezoelectric layer with a thickness of 0.5λ. An average TCF of 0 isindicated at a silicon dioxide thickness of about 0.3λ in FIG. 43B.These simulations suggest that a silicon dioxide of around 0.3λ canachieve a desirable TCF in such devices.

FIG. 44A is a graph of k² as a function of 5LN thickness for variousthicknesses of the silicon dioxide layer. This graph suggests thathaving a silicon dioxide layer over the IDT electrode on a 5LN layer canreduce k². FIG. 44B is a graph of v_(P-OPEN) as a function of 5LNthickness for various thicknesses of the silicon dioxide layer.

FIG. 45A illustrates a relationship between Qs and 5LN thickness forvarious silicon dioxide layer thicknesses. FIG. 45B illustrates arelationship between Qp and 5LN thicknesses for various silicon dioxidelayer thicknesses. The dots in FIGS. 45A and 45B indicate that a similarelastic wave device without the silicon substrate and the silicondioxide layer has Qs of 1798 and Qp of 40.5, respectively. Accordingly,the silicon substrate and the silicon dioxide layer of the elastic wavedevice 30 of FIG. 40 can boost Qp significantly in the elastic wavedevice 20 with a 5LN piezoelectric layer. Comparing FIG. 45B to FIG. 31Bindicates that having a silicon dioxide layer over the IDT electrode ona 5LN layer may not increase Qp as much as including a silicon dioxidelayer between a 5LN layer and a silicon substrate.

FIGS. 46A to 48B are graphs of simulations of an elastic wave device 30having a lithium tantalate piezoelectric layer with a 42° cut angle(42LT), a high velocity layer that is a silicon substrate, and atemperature compensating layer that is a silicon dioxide layer.

FIGS. 46A and 46B illustrate relationships between (1) TCF and thicknessof the silicon dioxide layer and (2) k² and thickness of the silicondioxide layer. FIG. 46A corresponds to a 42LT piezoelectric layer with athickness of 0.25λ. An average TCF of 0 is indicated at a silicondioxide thickness of about 0.2λ in FIG. 46A. FIG. 46B corresponds to a42LT piezoelectric layer with a thickness of 0.5λ. An average TCF of 0is indicated at a silicon dioxide thickness of about 0.25λ in FIG. 46B.These simulations suggest that a silicon dioxide of less than about0.25λ can achieve a desirable TCF in such devices.

FIG. 47A is a graph of k² as a function of 42LT thickness for variousthicknesses of the silicon dioxide layer. This graph suggests thathaving a silicon dioxide layer over the IDT electrode on a 42LT layercan reduce k². FIG. 47B is a graph of V_(P-OPEN) as a function of 42LTthickness for various thicknesses of the silicon dioxide layer.

FIG. 48A illustrates a relationship between Qs and 42LT thickness forvarious silicon dioxide layer thicknesses. FIG. 48B illustrates arelationship between Qp and 42LT thicknesses for various silicon dioxidelayer thicknesses. FIG. 48B indicates that having a silicon dioxidelayer over the IDT electrode and a silicon substrate can increase Qprelative to a similar elastic wave device without the silicon substrateand silicon dioxide layer. This graph also illustrates that it can bedesirable to have the 42LT layer thickness be less than about 0.8λ incertain instances.

FIG. 49A is graph of k² as a function of a cut angle of an LN layer inan elastic wave device 30 that includes an LN piezoelectric layer havinga thickness of 0.5λ, a high velocity layer that is a silicon substrate,and a temperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 49A indicates a maximum k² of about 30% at a cutangle of 10° and a silicon dioxide thickness of 0.

FIG. 49B is graph of v_(P-OPEN) as a function of a cut angle of an LNlayer in an elastic wave device 30 that includes an LN having athickness of 0.5λ, a high velocity layer that is a silicon substrate,and a temperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 49B indicates a maximum v₀ of about 4580 m/s ata cut angle of 40° and a silicon dioxide thickness of 0.2λ.

FIG. 49C is graph of Qs as a function of a cut angle of an LN layer inan elastic wave device 30 that includes an LN having a thickness of0.5λ, a high velocity layer that is a silicon substrate, and atemperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 49C indicates a maximum Qs of about 2100 at acut angle of 60° and a silicon dioxide thickness of 0.

FIG. 49D is graph of Qp as a function of a cut angle of an LN layer inan elastic wave device 30 that includes an LN having a thickness of0.5λ, a high velocity layer that is a silicon substrate, and atemperature compensating layer that is a silicon dioxide layer.Different curves on this graph correspond to different silicon dioxidelayer thicknesses. FIG. 49D indicates a maximum Qp of about 2560 at acut angle of 25° and a silicon dioxide thickness of 0.

FIGS. 50A to 50L illustrate admittance over frequency for an elasticwave device 30 with an LN piezoelectric layer having a thickness of0.5λ, temperature compensating layer that is a silicon dioxide layerhaving a thickness of 0.1λ, and a high velocity layer that is a siliconsubstrate for various cut angles of LN. FIG. 50F shows a relativelyclean frequency response without significant spurs for a cut angle of20°. These graphs indicate that cut angle in a range from about 15° to25° in such devices can achieve a relatively clean frequency response.

FIG. 51 is a plan view of the elastic wave device 30 of FIG. 40. FIG. 51illustrates that the IDT electrode 14 can be positioned between a firstgrating reflector 34 and a second grating reflector 36. The IDTelectrode 14, the first grating reflector 34, and the second gratingreflector 36 can function as a surface acoustic wave resonator. Any ofthe elastic wave devices 10, 20, or 40 can be similarly implemented.FIG. 51 illustrates that any of the temperature compensating layersdiscussed herein can be included above and/or below a portion of an IDTelectrode.

FIG. 52 is a cross-sectional view of an elastic wave device 40 accordingto an embodiment. As illustrated, the elastic wave device 40 includes apiezoelectric layer 12, an IDT electrode 14, a high velocity layer 16, afirst temperature compensating layer 22, and a second temperaturecompensating layer 32. The elastic wave device 40 is like the elasticwave device 20 of FIG. 21 except that the elastic wave device 40 alsoincludes a second temperature compensating layer 32 over the IDTelectrode 14 such that the IDT electrode 14 is between the piezoelectriclayer 12 and the temperature compensating layer 32. The elastic wavedevice 40 is like the elastic wave device 30 of FIG. 40 except that theelastic wave device 40 also includes a first temperature compensatinglayer 22 disposed between the high velocity layer 16 and thepiezoelectric layer 12. The elastic wave device 40 can have improvedinsensitivity for frequency dependence on the piezoelectric layerthickness relative to the elastic wave device 30 of FIG. 40.

Further simulations of LT/Si and LT/SiO₂/Si elastic wave devicesindicate that such devices have desirable k² values for an LT with a cutangle in a range from 0° to 30°. These simulations indicate that an LTlayer with a cut angle between 10° and 30° can be desirable. A maximumk² value was observed at a cut angle of about 20°. Other simulations ofLT/Si and LT/SiO₂/Si elastic wave devices indicate that such devices hashave desirable high velocity (v_(O)) values for such devices with an LTlayer with a cut angle in a range from 30° to 40°.

Any of the elastic wave devices discussed herein can be implemented in afilter, a duplexer or other multiplexer, or a frequency multiplexingcircuit (e.g., a diplexer or a triplexer).

FIGS. 53A to 53D are examples of filters that can benefit from theprinciples and advantages of the elastic wave devices discussed herein.By including an elastic wave device in accordance with the principlesand advantages discussed herein, such filters can realize improvedperformance, such as a higher quality factor, relative to filters thatinclude conventional elastic wave devices. Any suitable combination offeatures of these filters can be implemented together with each otherand/or in combination with any other embodiments discussed herein.

FIG. 53A is a schematic diagram of a filter 60 that includes an elasticwave device in accordance with the principles and advantages discussedherein. A filter that includes an elastic wave device can be referred toas an elastic device filter. As illustrated, the filter 60 is a ladderfilter of that includes series elastic wave devices 61, 63, and 65 andshunt surface acoustic wave devices 62 and 64. Each of the illustratedelastic wave devices can be a resonator. The elastic wave devices 61 to65 are arranged between an input port In and an output port Out. In someinstances, the filter 60 can be a transmit filter in which the inputport In is a transmit port and the output port Out is an antenna port.According to some other instances, the filter 60 can be a receive filterin which the input port In is an antenna port and the output port Out isa receive port.

One or more of the series elastic wave devices 61, 63, and 65 and/or oneor more of the shunt surface acoustic wave devices 62 and 64 can beimplemented in accordance with any suitable principles and advantagesdiscussed herein. One or more of the elastic wave devices 61 to 65 canbe surface acoustic wave devices. A filter that includes one or moresurface acoustic wave devices can be referred to as a surface acousticwave filter. While the filter 60 shows 5 elastic wave device resonatorsfor illustrative purposes, a filter can include any suitable number ofelastic device resonators for a particular application. For example, insome applications, an elastic wave device filter can include 3, 4, 6, 7,9, or more elastic wave devices.

FIG. 53B is a schematic diagram of a filter 60′ that includes an elasticwave device in accordance with the principles and advantages discussedherein. Any of the resonators of the filter 60′ can be implemented inaccordance with any suitable principles and advantages discussed herein.The filter 60′ is like the filter 60 of FIG. 53A except that the filter60′ includes a different number of resonators and also includes a loopcircuit. As illustrated, the filter 60′ includes an additional shuntsurface acoustic wave device 66 and an additional series surfaceacoustic wave device 67. The filter 60′ also includes a loop circuit 68.The loop circuit 68 is connected in parallel with the surface acousticwave resonators of the ladder circuit in FIG. 53B. The loop circuit 68can have a passing characteristic that allows a signal having afrequency in a certain frequency band inside a stopband of the laddercircuit of surface acoustic wave resonators to pass through the loopcircuit 68. The loop circuit 68 can output a loop signal in response tothe input signal at the input port In. The signals propagating throughthe ladder circuit and the loop circuit can include phase componentsopposite to each other in the certain frequency band inside thestopband.

FIG. 53C is a schematic diagram of a filter 60″ that includes an elasticwave device in accordance with the principles and advantages discussedherein. Any of the resonators of the filter 60″ can be implemented inaccordance with any suitable principles and advantages discussed herein.The filter 60″ is like the filter 60′ of FIG. 53B except that the filter60″ includes a particular example loop circuit 68′. As shown in FIG.53C, the loop circuit 68′ includes a first capacitor C1, IDT electrodes69, and a second capacitor C2. The illustrated capacitors and IDTelectrodes can be disposed on piezoelectric substrate. The piezoelectricsubstrate can be the same piezoelectric substrate on which theresonators of the ladder circuit are disposed. Accordingly, such apiezoelectric substrate can correspond to the layer structures shown inFIG. 1, FIG. 21, FIG. 40, or FIG. 52.

IDT electrodes 69 can be arranged as a transversal filter. The passingcharacteristic in the attenuation band can be adjusted by design of thistransversal filter, and the phase characteristic can be adjusted byadjusting a distance between IDT electrodes, so as to provide the loopcircuit 68′ with the phase characteristic opposite to that of laddercircuit. Each of IDT electrodes 69 can include a pair of comb-shapedelectrodes each including electrode fingers that interdigitate with eachother. Capacitances of the first and second capacitors C1 and C2,respectively, can be smaller than capacitances of IDT electrodes 69. Thecapacitance of the first capacitor C1 can be smaller than that of thesecond capacitor C2. An attenuation amount of the passing characteristicof loop circuit 68′ in the attenuation band can be adjusted by adjustingthe capacitances of first and second capacitors C1 and C2, respectively.The first and second capacitors C1 and C2 can be arranged so as to allowthe attenuation amount of the passing characteristic of the loop circuit68′ to be similar to an attenuation amount of the passing characteristicof ladder circuit.

With the phase characteristic of the loop circuit 68′ being opposite tothat of ladder circuit, an amplitude characteristic in the attenuationband of the ladder circuit can be substantially canceled. This canconsequently increase the attenuation amount in the attenuation band ofthe ladder circuit. Furthermore, a current that flows into the loopcircuit 68′ from the ladder circuit can be suppressed by selecting theelectrostatic capacitances of first and second capacitors C1 and C2,thereby having the function of protecting IDT electrodes 69 from damage.

FIG. 53D is a schematic diagram of a filter 60′ that includes an elasticwave device in accordance with the principles and advantages discussedherein. Any of the resonators of the filter 60′ can be implemented inaccordance with any suitable principles and advantages discussed herein.The filter 60′ is like the filter 60″ of FIG. 53C except that the filter60″ ‘includes a different loop circuit. As shown in FIG. 53D, the loopcircuit 68″ includes additional capacitors and IDT electrodes relativeto the loop circuit 68’. In particular, a third capacitor C3, and afourth capacitor C4 are included in the loop circuit 68″. The loopcircuit 68″ also includes IDT electrodes 69′ that includes more IDTelectrodes than IDT electrodes 69 of FIG. 53C.

FIGS. 54A to 54C are examples of duplexers that can benefit from theprinciples and advantages of the elastic wave devices discussed herein.By including an elastic wave device in accordance with the principlesand advantages discussed herein, such duplexers can realize improvedperformance, such as a higher quality factor, relative to duplexers thatinclude other conventional elastic wave devices. Any suitablecombination of features of these duplexers can be implemented togetherwith each other and/or in combination with any other embodimentsdiscussed herein.

FIG. 54A is a schematic diagram of a duplexer 70 that includes anelastic device in accordance with the principles and advantagesdiscussed herein. The duplexer 70 includes a transmit filter and areceive filter. The transmit filter and the receive filter are bothcoupled to a common port COM. The common port COM can be an antennaport. Any suitable number of elastic wave devices can be included in thetransmit filter and/or the receive filter of the duplexer 70.

The transmit filter is coupled between a transmit port TX and the commonport COM. The transmit filter is configured to filter a signal receivedat the transmit port TX that propagates to the common port COM. Thetransmit filter can include any suitable features of the filter 60 ofFIG. 53A. As illustrated, the transmit filter includes series elasticwave devices 61, 63, and 65 and shunt surface acoustic wave devices 62and 64. One or more of the series elastic wave devices 61, 63, and 65and/or one or more of the shunt surface acoustic wave devices 62 and 64can be implemented in accordance with any suitable principles andadvantages discussed herein.

The receive filter is coupled between the common port COM and thereceive port RX. The receive filter is configured to filter a signalreceived at the common port COM that propagates to the receive port RX.The receive filter can include any suitable features of the filter 60 ofFIG. 53A. As illustrated, the receive filter includes series elasticwave devices 71, 73, and 75 and shunt surface acoustic wave devices 72and 74. One or more of the series elastic wave devices 71, 73, and 75and/or one or more of the shunt surface acoustic wave devices 72 and 74can be implemented in accordance with any suitable principles andadvantages discussed herein.

Although FIG. 54A illustrates a duplexer 70, one or more elastic wavedevices in accordance with any suitable principles and advantagesdiscussed herein can be implemented in any suitable multiplexer. Amultiplexer can include any suitable number of acoustic wave filters.For example, the multiplexer can be a quadplexer with four filters, apentaplexer with five filters, a hexaplexer with six filters, anoctoplexer with eight filters, etc. In some instances, a multiplexer caninclude 2 to 16 elastic wave filters connected at a common node.

FIG. 54B is a schematic diagram of a duplexer 70′ that includes anelastic device in accordance with the principles and advantagesdiscussed herein. The duplexer 70′ is shown as being connected to anantenna 101. Any of the resonators of the duplexer 70′ can beimplemented in accordance with any suitable principles and advantagesdiscussed herein. The duplexer 70′ is like the duplexer 70 of FIG. 54Aexcept that the duplexer 70′ includes a different number of resonatorsin the transmit filter and includes a different receive filterarchitecture. As illustrated, the transmit filter of the duplexer 70′includes series SAW resonators 61, 63, 65, 67, and 79 and shunt SAWresonators 62, 64, 66, and 78. The receive filter of the duplexer 70′includes double mode SAW (DMS) resonators 111 and 112. The DMSresonators 111 and 112 are coupled to the antenna 101 by way of theseries SAW resonator 110 of the receive filter. The DMS resonators 111and/or 112 can include an elastic wave device in accordance with anysuitable principles and advantages discussed herein.

FIG. 54C is a schematic diagram of a duplexer 70″ that includes anelastic device in accordance with the principles and advantagesdiscussed herein. The duplexer 70″ is shown as being connected to anantenna 101. Any of the resonators of the duplexer 70″ can beimplemented in accordance with any suitable principles and advantagesdiscussed herein. The duplexer 70″ is like the duplexer 70′ of FIG. 54Bexcept that the duplexer 70″ additionally includes inductors L1 and L2,capacitors cap01, cap02, cap03, cap04, and cap05, and IDT electrodes113. The illustrated capacitors and IDT electrodes can implementfunctionality similar to the loop circuits discussed above. Theinductors L1 and L2 provide an inductive path to ground for shunt SAWresonators of the transmit filter.

A packaged module can include any of the elastic wave devices discussedherein. Some such packaged modules can also include a radio frequencyswitch and/or a power amplifier. The elastic wave devices discussedherein can be implemented in a variety of packaged modules. Some examplepackaged modules will now be discussed in which any suitable principlesand advantages of the elastic wave devices discussed herein can beimplemented. FIGS. 55, 56, and 57 are schematic block diagrams ofillustrative packaged modules according to certain embodiments. Anysuitable features discussed with reference to any of these packagedmodules can be implemented in combination with each other.

FIG. 55 is a schematic block diagram of a module 80 that includes afilter 82, a power amplifier 83, and a switch 84 in accordance with oneor more embodiments. The module 80 can include a package that enclosesthe illustrated elements. The filter 82, a power amplifier 83, and aswitch 84 can be disposed on a common packaging substrate. The packagingsubstrate can be a laminate substrate, for example. The filter 82 caninclude any suitable number of elastic wave devices implemented inaccordance with any suitable principles and advantages of the elasticwave devices discussed herein. The filter 82 can be included in aduplexer or other multiplexer. The switch 84 can be a radio frequencyswitch. The switch 84 can selectively electrically couple an output ofthe power amplifier 83 to the filter 82. In some instances, the switch84 can be a multi-throw switch that can provide the output of the poweramplifier to a selected filter of the plurality of filters of the module80.

FIG. 56 is a schematic block diagram of a module 85 that includes afilter 82, a power amplifier 83, a switch 84, and a second switch 86 inaccordance with one or more embodiments. The module 85 is like themodule 80 of FIG. 55, except that the module 85 includes an additionalswitch 86. The additional switch 86 can selectively electrically connectthe filter 82 to other RF circuitry. The additional switch 86 can be anantenna switch that can selectively electrically connect the filter 82to an antenna port.

FIG. 57 is a schematic block diagram of a module 90 that includes aduplexer 92, a power amplifier 83, and a first switch 84, a secondswitch 93, and a low noise amplifier 94 in accordance with one or moreembodiments. The module 90 is like the module 80 of FIG. 55, except inthe module 90 a duplexer is illustrated instead of a filter and themodule 90 includes receive circuitry. The illustrated receive circuitryincludes a switch 93 and a low noise amplifier 94. The low noiseamplifier 94 can amplify a radio frequency signal that is provided by areceive filter. The switch 93 can selectively electrically connect thelow noise amplifier 94 to the receive filter of the duplexer 92.

A wireless communication device, such as a mobile phone, can include oneor more elastic wave devices in accordance with any of the principlesand advantages discussed herein. FIG. 58 is a schematic block diagram ofa wireless communication device 100 that includes any suitable number ofelastic wave devices in accordance with one or more embodiments. Thewireless communication device 100 can be any suitable wirelesscommunication device. For instance, a wireless communication device 100can be a mobile phone, such as a smart phone. As illustrated, thewireless communication device 100 includes an antenna 101, an RF frontend 102 that includes filters 103, an RF transceiver 104, a processor105, and a memory 106. The antenna 101 can transmit RF signals providedby the RF front end 102. The antenna 101 can provide received RF signalsto the RF front end 102 for processing.

The RF front end 102 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplexer, or anysuitable combination thereof. The RF front end 102 can transmit andreceive RF signals associated with any suitable communication standards.Any of the elastic wave devices discussed herein can be implemented inone or more of the filters 103 of the RF front end 102.

The RF transceiver 104 can provide an RF signal to the RF front end 102for amplification and/or other processing. The RF transceiver 104 canalso process an RF signal provided by a low noise amplifier of the RFfront end 102. The RF transceiver 104 is in communication with theprocessor 105. The processor 105 can be a baseband processor. Theprocessor 105 can provide any suitable baseband processing functions forthe wireless communication device 100. The memory 106 can be accessed bythe processor 105. The memory 106 can store any suitable data for thewireless communication device 100.

Any of the principles and advantages discussed herein can be applied toother systems, modules, chips, elastic wave devices, filters, duplexers,multiplexers, wireless communication devices, and methods not just toembodiments described herein. The elements and operations of the variousembodiments described above can be combined to provide furtherembodiments. Some of the embodiments described above have providedexamples in connection with elastic wave devices, such as SAWresonators. However, the principles and advantages of the embodimentscan be used in connection with any other systems, apparatus, or methodsthat benefit could from any of the teachings herein. Any of theprinciples and advantages discussed herein can be implemented inassociation with radio frequency circuits configured to process signalsin a range from about 30 kHz to 300 GHz, such as in a range from about450 MHz to 6 GHz. For instance, any of the filters discussed herein canfilter signals in a range from about 30 kHz to 300 GHz, such as in arange from about 450 MHz to 6 GHz.

The performance of elastic wave devices discussed herein can bedesirable in RF systems that support carrier aggregation and/ormulti-input and multi-output (MIMO) communications. User demand fordownlink capacity can be insatiable for multimedia content streaming. Toincrease capacity, different data-streams can be sent using multipleantennas and/or downlink carrier aggregation can be implemented bycombining the channel bandwidth available from different frequency bandsand/or different frequency sub bands. With elastic wave devicesdiscussed herein, such RF systems can have enhanced performance.

FIG. 59 is a schematic diagram of an RF system 120 that includes afilter with an elastic wave device in accordance with one or moreembodiments. RF system 120 supports carrier aggregation and MIMOfunctionality. As illustrated, the RF system 120 includes a firstantenna 139, a second antenna 141, and an RF front end. The illustratedRF front end includes a high band transmit and receive module 122, a midband transmit and receive module 132, a high band and mid band receivemodule 140 and a triplexer 138. Although not illustrated in FIG. 59, theRF front end also includes a low band transmit and receive module. Theillustrated RF system 120 can transmit and receive signals of a varietyof frequency bands, including low band (LB), mid band (MB), and highband (HB) signals. For example, the RF system 120 can process one ormore LB signals having a frequency of 1 GHz or less, one or more MBsignals having a frequency between 1 GHz and 2.3 GHz, and one or more HBsignals having a frequency greater than 2.3 GHz. Examples of LBfrequencies include, but are not limited to Band 8, Band 20, and Band26. Examples of MB frequencies include, but are not limited to, Band 1,Band 3, and Band 4. Examples of HB frequencies include, but are notlimited to, Band 7, Band 38, and Band 41.

In the illustrated RF system 120, the high band transmit and receivemodule 122 is electrically coupled to the first antenna 139 by way oftriplexer 138. The first antenna 139 is implemented to handle LB, MB andHB signals. The first antenna 139 can transmit and receive carrieraggregated signals. The illustrated high band transmit and receivemodule 122 includes a power amplifier 123, duplexers 124A and 124B, lownoise amplifiers 125A and 125B, and antenna switch 126. Filters of theseduplexers can be arranged to filter HB signals within differentfrequency bands. These filters can be band pass filters as illustrated.Any resonators of the duplexers 124A and/or 124B can be implemented inaccordance with any suitable principles and advantages discussed herein.The high band transmit and receive module 122 can generate HB signalsfor transmission by the first antenna 139 and process HB signalsreceived by the first antenna 139. Any suitable number of signal pathsfor transmit and/or receive can be implemented in the high band transmitand receive module 122.

As illustrated, the mid band transmit and receive module 132 iselectrically coupled to the first antenna 139 by way of triplexer 138.The illustrated mid band transmit and receive module 132 includes apower amplifier 133, duplexers 134A and 134B, low noise amplifiers 135Aand 135B, and antenna switch 136. Filters of these duplexers can bearranged to filter MB signals within different frequency bands. Thesefilters can be band pass filters as illustrated. Any resonators of theduplexers 134A and/or 134B can be implemented in accordance with anysuitable principles and advantages discussed herein. The mid bandtransmit and receive module 132 can generate BB signals for transmissionby the first antenna 139 and process MB signals received by the firstantenna 139. Any suitable number of signal paths for transmit and/orreceive can be implemented in the mid band transmit and receive module132.

The second antenna 141 can receive HB and MB signals. The second antenna141 can be a diversity antenna and the first antenna 139 can be aprimary antenna. The received signals can be processed by the mid bandand high band MIMO receive module 140. The illustrated mid band and highband MIMO receive module 140 includes an antenna switch 142, receivefilters 143A, 143B, 143C, and 143D, and low noise amplifiers 144A, 144B,144C, and 144D. These receive filters can be arranged to filter HBsignals or MB signals within different frequency bands. These receivefilters can be band pass filters as illustrated. Any resonators of thereceive filters 143A to 143D can be implemented in accordance with anysuitable principles and advantages discussed herein.

The illustrated RF system 120 can support downlink MIMO for both HB andMB. Although the RF system 120 of FIG. 59 includes two antennas forreceiving HB and MB signals, the RF system 120 can be adapted to includeadditional antennas to provide MIMO of a higher order. In one example,additional antennas and modules can be implemented to support 4×4 RXMIMO for MB and HB signals.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as semiconductor die and/or packaged radiofrequency modules, electronic test equipment, uplink wirelesscommunication devices, personal area network communication devices, etc.Examples of the consumer electronic products can include, but are notlimited to, a mobile phone such as a smart phone, a wearable computingdevice such as a smart watch or an ear piece, a telephone, a television,a computer monitor, a computer, a router, a modem, a hand-held computer,a laptop computer, a tablet computer, a personal digital assistant(PDA), a microwave, a refrigerator, a vehicular electronics system suchas an automotive electronics system, a stereo system, a DVD player, a CDplayer, a digital music player such as an MP3 player, a radio, acamcorder, a camera such as a digital camera, a portable memory chip, awasher, a dryer, a washer/dryer, peripheral device, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context requires otherwise, throughout the description andthe claims, the words “comprise,” “comprising,” “include,” “including,”and the like are to generally be construed in an inclusive sense, asopposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to.” The word “coupled,” asgenerally used herein, refers to two or more elements that may be eitherdirectly coupled to each other, or coupled by way of one or moreintermediate elements. Likewise, the word “connected,” as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description of CertainEmbodiments using the singular or plural may also include the plural orsingular, respectively. The word “or” in reference to a list of two ormore items, is generally intended to encompass all of the followinginterpretations of the word: any of the items in the list, all of theitems in the list, and any combination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding whether thesefeatures, elements and/or states are included or are to be performed inany particular embodiment.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel methods, devices, apparatus,and systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in theform of the methods, apparatus, and systems described herein may be madewithout departing from the spirit of the disclosure. For example,circuit blocks and/or device structures described herein may be deleted,moved, added, subdivided, combined, and/or modified. Each of thesecircuit blocks and/or device structure may be implemented in a varietyof different ways. The accompanying claims and their equivalents areintended to cover any such forms or modifications as would fall withinthe scope and spirit of the disclosure.

What is claimed is:
 1. An elastic wave device comprising: apiezoelectric layer having a cut angle in a cut angle range from −10° to60°; an interdigital transducer electrode on the piezoelectric layer,the interdigital transducer electrode configured to generate an elasticwave having a wavelength of λ, and the piezoelectric layer having athickness in a thickness range from 0.35λ to 0.8λ; and a high velocitylayer in physical contact with the piezoelectric layer, the highvelocity layer having a higher bulk velocity than a velocity of theelastic wave.
 2. The elastic wave device of claim 1 wherein thepiezoelectric layer includes a lithium niobate layer.
 3. The elasticwave device of claim 1 wherein the piezoelectric layer includes alithium tantalate layer.
 4. The elastic wave device of claim 1 whereinthe high velocity layer is a silicon layer.
 5. The elastic wave deviceof claim 1 wherein the cut angle is in a range from −10° to 30°.
 6. Theelastic wave device of claim 1 wherein the interdigital transducerelectrode has a thickness in a second thickness range from 0.02λ to0.1λ.
 7. The elastic wave device of claim 1 further comprising atemperature compensating layer having a positive temperature coefficientof frequency, the interdigital transducer electrode being disposedbetween the temperature compensating layer and the piezoelectric layer.8. The elastic wave device of claim 7 wherein the temperaturecompensating layer has a thickness of less than 0.5λ.
 9. An elastic wavedevice comprising: a lithium niobate layer having a cut angle in a cutangle range from −10° to 60°; an interdigital transducer electrode onthe lithium niobate layer, the interdigital transducer electrodeconfigured to generate an elastic wave having a wavelength of λ, and thelithium niobate layer having a thickness in a thickness range from 0.35,to 0.8λ; and a silicon substrate in physical contact with the lithiumniobate layer.
 10. The elastic wave device of claim 9 wherein the cutangle is in a range from 15° to 35°.
 11. The elastic wave device ofclaim 9 wherein the thickness of the lithium niobate layer is in a rangefrom 0.4λ to 0.75λ.
 12. The elastic wave device of claim 9 wherein theinterdigital transducer electrode includes has a thickness in a secondthickness range from 0.02λ to 0.1λ.
 13. The elastic wave device of claim9 further comprising a temperature compensating layer having a positivetemperature coefficient of frequency, the interdigital transducerelectrode being disposed between the temperature compensating layer andthe piezoelectric layer.
 14. An elastic wave device comprising: apiezoelectric layer having a cut angle in a cut angle range from −10° to60°; an interdigital transducer electrode on the piezoelectric layer,the interdigital transducer electrode configured to generate an elasticwave having a wavelength of λ, and the piezoelectric layer having athickness in a thickness range from 0.25λ to 0.8λ; a silicon layerconfigured to inhibit the elastic wave from leaking from thepiezoelectric layer at anti-resonance, the piezoelectric layer beingdisposed between the silicon layer and the interdigital transducerelectrode; and a temperature compensating layer having a positivetemperature coefficient of frequency, interdigital transducer electrodebeing disposed between the temperature compensating layer and thepiezoelectric layer.
 15. The elastic wave device of claim 14 wherein thetemperature compensating layer has a thickness of less than 0.5λ. 16.The elastic wave device of claim 14 wherein the temperature compensatinglayer includes silicon dioxide.
 17. The elastic wave device of claim 14wherein the cut angle is between 15° and 35°.
 18. The elastic wavedevice of claim 14 wherein the interdigital transducer electrode has athickness between 0.02λ and 0.1λ.
 19. The elastic wave device of claim14 wherein the piezoelectric layer is a lithium niobate layer.
 20. Theelastic wave device of claim 14 wherein the silicon layer is in physicalcontact with the piezoelectric layer.